Research Articles (Veterinary Tropical Diseases)

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Decoding the anomalies : a genome-based analysis of Bacillus cereus group strains closely related to Bacillus anthracis
(Frontiers Media, 2025-02) Magome, Thuto Gomolemo; Surleac, Marius; Hassim, Ayesha; Bezuidenhout, Cornelius Carlos; Van Heerden, Henriette; Lekota, Kgaugelo Edward
INTRODUCTION : The Bacillus cereus group encompasses a complex group of closely related pathogenic and non-pathogenic bacterial species. Key members include B. anthracis, B. cereus, and B. thuringiensis organisms that, despite genetic proximity, diverge significantly in morphology and pathogenic potential. Taxonomic challenges persist due to inconsistent classification methods, particularly for B. cereus isolates that resemble B. anthracis in genetic clustering. METHODS : This study investigated B. cereus group isolates from blood smears of animal carcasses in Kruger National Park, uncovering an unusual isolate with B. cereus features based on classical microbiological tests yet B. anthracis-like genomic similarities with an Average Nucleotide Identity (ANI) of ≥95%. Using comparative genomics, pan-genomics and whole genome Single Nucleotide Polymorphism (wgSNP) analysis, a total of 103 B. cereus group genomes were analyzed, including nine newly sequenced isolates from South Africa and a collection of isolates that showed some classification discrepancies, thus classified as “anomalous.” RESULTS AND DISCUSSION : Of the 36 strains identified as B. anthracis in GenBank, 26 clustered phylogenetically with the four confirmed B. anthracis isolates from South Africa and shared 99% ANI. Isolates with less than 99% ANI alignment to B. anthracis exhibited characteristics consistent with B. cereus and/or B. thuringiensis, possessing diverse genetic profiles, insertion elements, resistance genes, and virulence genes features, contrasting with the genetic uniformity of typical B. anthracis. The findings underscore a recurrent acquisition of mobile genetic elements within B. cereus and B. thuringiensis, a process infrequent in B. anthracis. CONCLUSION : This study highlights the pressing need for standardized taxonomic criteria in B. cereus group classification, especially as anomalous isolates emerge. This study supports the existing nomenclature framework which offers an effective solution for classifying species into genomospecies groups. We recommend isolates with ANI ≥99% to standard reference B. anthracis be designated as typical B. anthracis in GenBank to maintain taxonomic clarity and precision.
Rhinoceromics : a multi-amplicon study with clinical markers to transferrin saturation levels in ex-situ black rhinoceros (Diceros bicornis michaeli)
(Frontiers Media, 2025-05) Bruins-van Sonsbeek, Linda G.R.; Verschuren, Martie C.M.; Kaal, Sonja; Lindenburg, Peter W.; Rodenburg, Kees (C.) W.; Clauss, Marcus; Speksnijder, Arjen G.C.L.; Rutten, Victor P.M.G.; Bonnet, Bas F.J.; Wittink, Floyd
Iron overload disorder (IOD) is a common condition in ex-situ black rhinoceroses (Diceros bicornis), although it has not been reported in the wild. This study aimed to gain a deeper understanding of the relationship between 25-hydroxy vitamin D [25(OH)D], inflammatory markers, insulin levels, the gut microbiome, dietary components, and transferrin saturation (TS) in ex-situ black rhinoceroses. Blood and fecal samples from 11 black rhinoceroses at five different European zoological institutions were monitored over a 1-year period. Inflammatory markers such as interleukin 6 (IL-6), serum amyloid A (SAA), interferon γ (IFN-γ), and tumor necrosis factor α (TNF-α) were analyzed. Our study corroborates the findings of previous research, which demonstrated that insulin, inflammatory markers, and TS% are higher in ex-situ black rhinoceroses compared to published wild ranges. Our data show no correlations between insulin, 25(OH)D, TS%, inflammatory markers, or short-chain fatty acids (SFCAs). Serum 25(OH)D exhibited significantly higher levels in summer than in winter. Transferrin saturation was influenced by age, which is consistent with previous studies. The microbiome did not differ significantly among individuals, institutions, sex, or season, unlike the mycobiome, which exhibited significant differences across institutions. The impact of the mycobiome differences on the physiology of the animals could not be determined from this study.
Evaluating the efficacy of bioelectrical impedance analysis using machine learning models for the classification of goats exposed to Haemonchosis
(Frontiers Media, 2025-05) Siddique, Aftab; Batchu, Phaneendra; Shaik, Arshad; Gurrapu, Priyanka; Erukulla, Tharun Tej; Ellington, Cornileus; Villa, Andrea L. Rubio; Brown, Davia; Mahapatra, Ajit; Panda, Sudhanshu; Morgan, Eric; Van Wyk, Jan Aucamp; Shapiro-Ilan, David; Kannan, Govind; Terrill, Thomas H.
Rapid identification and assessment of animal health are critical for livestock productivity, especially for small ruminants like goats, which are highly susceptible to blood-feeding gastrointestinal nematodes, such as Haemonchus contortus. This study aimed at establishing proof of concept for using bioelectrical impedance analysis (BIA) as a non-invasive diagnostic tool to classify animals at different levels of Haemonchosis. A cohort of 94 intact Spanish bucks (58 healthy; 36 Unhealthy; naturally infected with H. contortus) was selected to evaluate the efficacy of BIA through the measurement of resistance (Rs) and electrical reactance (Xc). Data were collected from live goats using the CQR 3.0 device over multiple time points. The study employed several machines learning models, including Support Vector Machines (SVM), Backpropagation Neural Networks (BPNN), k-Nearest Neighbors (K-NN), XGBoost, and Keras deep learning models to classify goats based on their bioelectrical properties. Among the classification models, SVM demonstrated the highest accuracy (95%) and F1-score (96%), while K-NN showed the lowest accuracy (90%). For regression tasks, BPNN outperformed other models, with a nearly perfect R2 value of 99.9% and a minimal Mean Squared Error (MSE) of 1.25e-04, followed by SVR with an R2 of 96.9%. The BIA data revealed significant differences in Rs and Xc between lightly and more heavily Unhealthy goats, with the latter exhibiting elevated resistance values, likely due to dehydration and tissue changes resulting from Haemonchosis. These findings highlight the potential of BIA combined with machine learning to develop a scalable, rapid, and non-invasive diagnostic tool for monitoring small ruminant health, particularly in detecting parasitic infections like H. contortus. This approach could improve herd management, reduce productivity losses, and enhance animal welfare.
Factors influencing the frequency, knowledge, attitudes and practices of antibiotic use in commercial layer chicken farms, Tanzania
(Frontiers Media, 2025-04) Mdemu, Siha; Matondo, Augustine B.; Christensen, Jens Peter; Amasha, Ahmed E.; Ngowi, Helena A.; Westwood, Erica; Ochai, Sunday Ochonu; Nonga, Hezron E.; Osbjer, Kristina; Mdegela, Robinson H.
INTRODUCTION : Indiscriminate use of veterinary antibiotics significantly contributes to the current antibiotic resistance in the world. The primary objective of this study was to explore the factors that could influence knowledge, attitudes and practices of antibiotic use in commercial layer farms. METHODS : A cross-sectional study was conducted to evaluate antibiotic use patterns and their associated factors among layer chicken farmers in Tanzania. The study surveyed 205 farmers randomly selected from three regions: Unguja, Morogoro, and Dar es Salaam. Data were analysed using descriptive statistics, while negative binomial and multiple linear regression models were employed to identify factors influencing antibiotic usage patterns. RESULTS : A widespread use of antibiotics was revealed, with 97.1% of farmers using antibiotics for treatment, prophylaxis and/or increasing egg productivity. The most commonly used antibiotics were oxytetracycline (63%), doxycline-tylosin combination (29.8%) and enrofloxacin (22.4%). Notably, 95.6% of farmers reported that they do not observe withdrawal periods. Assessment of farmers' knowledge, attitudes, and practices yielded mean scores of 55.5%, 69.1% and 50.9% respectively. Furthermore, older adults and individuals with primary education were more likely to have higher attitude scores. Geographic location and flock size are among other factors that are likely to influence knowledge and attitudes towards antibiotic use. Higher frequency of antibiotic use was significantly associated with young adults, medium-scale farm operators, and farmers in Morogoro region (compared to the other two regions). CONCLUSION : The frequency, knowledge, attitude and practices related to the use of antibiotics were affected by scale of production, location, age, and education. These findings provide insights into antibiotic stewardship among layer farmers that could suggest future multifaceted interventions to promote prudent use of antibiotics, hence mitigating risk of antibiotic resistance.
First detection of Amblyomma lepidum (Dönitz, 1909) in Zimbabwe
(Springer, 2025-04) Smit, Andeliza; Mandara, Stephen; Dlamkile, Zinathi; Morar-Leather, Darshana; Bosman, Anna-Mari; Neves, Luís C.B.G.
Herewith we present the first detection of Amblyomma lepidum (Dönitz, 1909) on cattle in Zimbabwe. Zimbabwe’s smallholder farmers rely heavily on their livestock, mainly cattle and goats. Even though great importance is placed on cattle farming, no systematic surveillance of tick and tick-borne diseases is currently being conducted in the country. Forming part of the Amblyomma genus, A. lepidum is a brightly ornate tick with great vector potential, which could have harmful effects on cattle and cattle farming in Zimbabwe. This report documents the presence of both male and female A. lepidum ticks that were morphologically identified, and with the use of two ribosomal genes, were molecularly characterised as A. lepidum. Hypotheses can be made as to how this tick was introduced into Zimbabwe; however, its presence highlights the need for a systematic surveillance programme to track not only new introductions, such as the aforementioned, but the current distribution of this tick population in Zimbabwe.
Elimination of dog-mediated human rabies : scientific tools, one health and partnerships
(Office International des Epizooties, 2024-12) Blumberg, Lucille Hellen
A world free of dog-mediated human rabies by 2030 would be an outstanding achievement. This ambitious goal for a neglected tropical disease, set by the World Organisation for Animal Health (WOAH), the World Health Organization, the Food and Agriculture Organization of the United Nations and the Global Alliance for Rabies Control together with partners and countries, has a clear and achievable pathway to success. In the 100 years since the inception of WOAH, many scientific tools have been developed to support the elimination of dog-mediated rabies. In addition to these tools, engaging communities and health workers to build awareness to prevent bite exposures, managing dog populations and ensuring herd immunity through dog vaccination are key to achieving the elimination goals. The provision of post-exposure prophylaxis and care for exposed victims are important interventions on the human side. Success in eradicating rabies will require applying a One Health approach, an integrative and systemic approach to health grounded in the understanding that human health is closely linked to animal and environmental health. Political commitment and availability of adequate resources are key to achieving the Zero by 2030 goal.
A One Health perspective on Salmonella enterica Serovar Infantis, an emerging human multidrug-resistant pathogen
(Centers for Disease Control and Prevention (CDC), 2024-04) Mattock, Jennifer; Chattaway, Marie Anne; Hartman, Hassan; Dallman, Timothy J.; Smith, Anthony Marius; Keddy, Karen H.; Petrovska, Lilijana; Manners, Emma J.; Duze, Sanelisiwe T.; Smouse, Shannon; Tau, Nomsa; Timme, Ruth; Baker, Dave J.; Mather, Alison E.; Wain, John; Langridge, Gemma C.
Salmonella enterica serovar Infantis presents an ever increasing threat to public health because of its spread throughout many countries and association with high levels of antimicrobial resistance (AMR). We analyzed whole genome sequences of 5,284 Salmonella Infantis strains from 74 countries, isolated during 1989–2020 from a wide variety of human, animal, and food sources, to compare genetic phylogeny, AMR determinants, and plasmid presence. The global Salmonella Infantis population structure diverged into 3 clusters: a North American cluster, a European cluster, and a global cluster. The levels of AMR varied by Salmonella Infantis cluster and by isolation source; 73% of poultry isolates were multidrug resistant, compared with 35% of human isolates. This finding correlated with the presence of the pESI megaplasmid; 71% of poultry isolates contained pESI, compared with 32% of human isolates. This study provides key information for public health teams engaged in reducing the spread of this pathogen.
Identification of ticks and tick-borne pathogens of wildlife necropsy cases submitted to the SANBI National Zoological Gardens, South Africa
(Elsevier, 2024-10) Khumalo, Nozipho; Ledwaba, Maphuti Betty; Labuschagne, Kim; Vorster, Ilse; Oosthuizen, Marinda C.; Mwale, Monica; Chaisi, Mamohale E.
Ticks are arachnid blood-feeding parasites, which infest livestock, wildlife, and humans, transmitting medically and veterinary significant pathogens. Their biodiversity and distribution in wild animals remains complex. This study analysed archived tick samples (n = 48) from the South African Biodiversity Institute (SANBI) Wildlife Biobank utilizing morphology and genetic analyses of the 16S rRNA and COI (DNA barcoding) mitochondrial genes to identify ticks collected among 13 vertebratesavian, reptilian, and mammalian host species. The specimens came from nine localities including nature reserves and captive facilities (zoological garden) in South Africa, Namibia, and Botswana. These ticks were also assessed for associated pathogens with the reverse line blot (RLB) hybridization assay. Seven tick genera, Amblyomma, Hyalomma, Haemaphysalis, Ixodes, Rhipicephalus, Rhipicentor, and Otobius were identified, with Amblyomma being the most prevalent (22.9 %) in our sample set. Obtained sequences were 95–100 % similar to published records of tick species collected from wild and domestic animals, as well as those collected from vegetation, from different southern African areas. However, tick specimens (n = 3) identified morphologically as Hyalomma truncatum, Rhipicephalus e. evertsi, and R. simus, were, on a molecularly level, more closely related to their sister taxa (H. glabrum, R. e. mimeticus, and R. gertrudae, respectively) suggesting a need for taxonomic verification. With the RLB hybridization assay, six samples reacted with the Ehrlichia/Anaplasma genus-specific probe, while two reacted with the Theileria/Babesia genus-specific probe. Sequencing of the RLB amplicons targeting the 18S rRNA gene (n = 2) indicated 100 % similarity to Hepatozoon fitzsimonsi, while one was closely related to He. ingwe with 99.39 % similarity. The results show that wildlife harbour different tick species, and pathogen detection identified novel genotypes, indicating wildlife as potential pathogens reservoirs. This study enhances our understanding of tick biodiversity, distribution and highlights wildlife's role in harbouring diverse tick species and novel pathogens.
Development and validation of a real-time PCR assay, and phylogenetic analysis of Anaplasma platys
(Elsevier, 2025-07) Nkosi, Nokuzola Faith; Byaruhanga, Charles; Arega, Sintayehu M.; Conan, Anne; Knobel, Darryn Leslie; Oosthuizen, Marinda C.; Quan, Melvyn; melvyn.quan@up.ac.za
Anaplasmosis is a tick-borne disease caused by species of the genus Anaplasma. In dogs anaplasmosis is caused by Anaplasma phagocytophilum and Anaplasma platys. These bacteria are in the family Anaplasmataceae in the order Rickettsiales. Anaplasma platys is a Gram-negative bacterium that is of public health and veterinary importance. This pathogen exclusively infects platelets and causes infectious cyclic thrombocytopenia in dogs. Infection occurs through the bite of an infected ixodid tick, Rhipicephalus sanguineus, which is the principal vector and is also known to transmit Ehrlichia canis, another bacteria of veterinary importance. Our group recently reported on the developed group-specific Ehrlichia/Anaplasma primers and the A. platys-specific TaqMan® Minor Groove Binder probe for multiplexing purposes. This study validated the A. platys TaqMan® PCR assay targeting the 16S rRNA gene. Furthermore, phylogenetic analysis was used to characterize A. platys. The assay efficiency was 94.9 %, and the 95 % limit of detection (LOD) was 5.08 A. platys plasmid copies/μl blood with a 95 % confidence interval of 3.1–10.2. The assay did not cross-react when tested against other haemoparasites. The phylogenetic characterization of the Mnisi community samples revealed that the A. platys sequences from this area grouped with other A. platys sequences from South Africa and other countries, including India, Zambia, Taiwan, Thailand, and Croatia. The developed TaqMan® qPCR assay will be a valuable tool for the early diagnosis of A. platys by preventing inappropriate use of antibiotics and alleviating potential emerging antimicrobial resistance. Additionally, early detection and administration of the correct antibiotics speed recovery time.
Roles of host and environment in shift of primary anthrax host species in Kruger National Park
(Public Library of Science, 2024-12-06) Ochai, Sunday Ochonu; Snyman, Lourens F.; Dolfi, Amelie C.; Ramoelo, Abel; Reilly, Brian K.; Botha, Judith M.; Dekker, Edgar H.; Van Schalkwyk, Ockert Louis; Kamath, Pauline L.; Archer, Emma Rosa Mary; Turner, Wendy C.; Van Heerden, Henriette
Environmental and climatic factors, as well as host demographics and behaviour, significantly influence the exposure of herbivorous mammalian hosts to pathogens such as Bacillus anthracis, the causative agent of anthrax. Until the early 1990s in Kruger National Park (KNP), kudu (Tragelaphus strepsiceros) was the host species most affected by anthrax, with outbreaks occurring predominantly in the dry season, particularly during drought cycles. However, the most affected host species has shifted to impala (Aepyceros melampus), with more frequent anthrax outbreaks during the wet season. This study investigates the roles of environmental variation and other host species in this shift. Temporal trends in environmental variables such as precipitation, soil moisture, temperature, and normalised difference vegetation index (NDVI) were analyzed in relation to anthrax occurrence (presence/ absence and counts). Additionally, correlations between host species' densities and anthrax mortalities over time were examined. Anthrax cases in 1990 were concentrated in the central and northern regions of KNP (excluding Pafuri), primarily affected kudus; while subsequent mortalities affected mostly impala and were restricted to the far north, in Pafuri. Significant correlations were found between kudu anthrax mortality and a decrease in NDVI, average temperature, SPI-6 and SPI-12 (Standardised Precipitation Index in various time intervals. Conversely, anthrax occurrence in impalas was associated with a decline in SPI-3, and temperature rise, with increased mortality during the rainy season. Elephant density correlated negatively with kudu mortality, but a positive correlation with both impala mortality and impala density. The study concludes that environmental variables and species' densities may alter the diversity and frequency of hosts exposed to B. anthracis. Climate extremes and alterations therein may exacerbate anthrax severity by modifying species susceptibility and their probability of exposure over time.
Epidemiology of Echinococcus granulosus sensu lato in the Greater Horn of Africa : a systematic review
(Public Library of Science, 2024-01-25) Aregawi, Weldegebrial G.; Levecke, Bruno; Ashenafi, Hagos; Byaruhanga, Charles; Kebede , Nigatu; Mulinge , Erastus; Wassermann, Marion; Romig, Thomas; Dorny, Pierre; Dermauw, Veronique
BACKGROUND : Cystic echinococcosis (CE) is a neglected zoonotic disease that is caused by Echinococcus granulosus sensu lato (s.l.), the life cycle of which involves multiple hosts. We conducted a systematic review (SR) on E. granulosus s.l. in the Greater Horn of Africa (GHA), to provide a picture of its recent epidemiology across all hosts. METHODS : For this SR, conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement, five electronic databases, as well experts in the region were consulted to retrieve records published between 2000 and 2022, reporting the presence of E. granulosus s.l. infections in any natural host in the GHA (Djibouti, Eritrea, Ethiopia, Kenya, Sudan, Somalia, South Sudan, Tanzania and Uganda). PRINCIPAL FINDINGS : A total of 247 records were retained, describing the presence of E. granulosus s.l. throughout the GHA, except for Djibouti. Only few population surveys on human CE were conducted in the area, with the prevalence ranging between 0.3 and 11.3%. In animals, the reported prevalence ranged up to 61.6% in camels, 88.4% in cattle; 65.2% in goats, 9.9% in pigs, 67.8% in sheep and 94.5% in dogs. In addition, E. granulosus s.l. was also reported in wildlife. A total of five species were reported in the different hosts, namely E. granulosus sensu stricto (G1, G3, GOmo), E. canadensis (G6/7), E. ortleppi (G5), E. felidis, and E. equinus (G4). CONCLUSIONS : We confirm that E. granulosus s.l. is prevalent throughout the GHA. Nevertheless, despite our efforts to screen grey literature, an accurate assessment of the epidemiology in GHA remains challenging, due to the lack of combined host, in-depth risk factor and behavioural studies, as well as the wide diversity in subpopulations studied and diagnostic tools used. Interdisciplinary and transboundary partnerships would be essential for the design of effective control strategies, tuned to the GHA setting.
The importance of estimating the burden of disease from foodborne transmission of Trypanosoma cruzi
(Public Library of Science, 2024-02-08) Robertson, Lucy J.; Havelaar, Arie H.; Keddy, Karen H.; Devleesschauwer, Brecht; Sripa, Banchob; Torgerson, Paul R.
Chagas disease (ChD), caused by infection with the flagellated protozoan, Trypanosoma cruzi, has a complicated transmission cycle with many infection routes. These include vector-borne (via the triatomine (reduviid bug) vector defecating into a skin abrasion, usually following a blood meal), transplacental transmission, blood transfusion, organ transplant, laboratory accident, and foodborne transmission. Foodborne transmission may occur due to ingestion of meat or blood from infected animals or from ingestion of other foods (often fruit juice) contaminated by infected vectors or secretions from reservoir hosts. Despite the high disease burden associated with ChD, it was omitted from the original World Health Organization estimates of foodborne disease burden that were published in 2015. As these estimates are currently being updated, this review presents arguments for including ChD in new estimates of the global burden of foodborne disease. Preliminary calculations suggest a burden of at least 137,000 Disability Adjusted Life Years, but this does not take into account the greater symptom severity associated with foodborne transmission. Thus, we also provide information regarding the greater health burden in endemic areas associated with foodborne infection compared with vector-borne infection, with higher mortality and more severe symptoms. We therefore suggest that it is insufficient to use source attribution alone to determine the foodborne proportion of current burden estimates, as this may underestimate the higher disability and mortality associated with the foodborne infection route.
Seroprevalence and risk factors of brucellosis in pastoralists and their livestock in Central Equatoria State, South Sudan
(Public Library of Science, 2024-12-19) Lita, Emmanuel P.; Ochi, Erneo B.; Misinzo, Gerald; Van Heerden, Henriette; Katani, Robab; Godfroid, Jacques; Mathew, Coletha
BACKGROUND : Brucellosis poses serious public health implications and substantial economic losses in pastoral rural settings in South Sudan. In humans, brucellosis is almost always originating from animals. Current literature provides scant data regarding the seroprevalence of brucellosis in South Sudan. This cross-sectional study investigates the seroprevalence of brucellosis among the pastoral community and livestock and identifies risk factors for the disease from two Counties, Terekeka and Juba in Central Equatoria State (CES), South Sudan. METHODOLOGY : A total of 986 sera; from humans (n = 143), cattle (n = 478), sheep (n = 86), and goats (n = 279) were randomly collected from 17 cattle camps in CES. Sera for the humans, cattle and goats were screened for Brucella-specific antibodies using Rose Bengal plate test (RBPT) and further confirmed by competitive enzyme-linked immunosorbent assay (c-ELISA) in series due to the cost of testing. All the sera from sheep were tested in parallel using RBPT and c-ELISA as the sheep samples were few and were all tested negative on the RBPT. A camp was considered positive when at least one animal of either species tested positive on the c-ELISA. A structured questionnaire was used to collect information on potential individual and herd level risk factors. Univariate analysis using binary logistic regression with a confidence interval of 95% at a p-value of ≤ 0.05 was used to identify the association between the potential individual risk factors and Brucella seropositivity. The investigated risk factors for livestock included age, sex, species, prior abortion history, retained placenta, parity, and reproductive status. Variables found to have associations in univariate analysis (p = 0.25) with Brucella seropositivity were further included in multivariable logistic regression. The risk factors investigated for humans included, gender, age, educational level, occupation, marital status, drinking of raw milk, aiding female animals during delivery, eating undercooked meat and blowing of air into the cow’s uterus through the vagina, a practice in South Sudan. RESULTS : The study revealed seroprevalence of 21.7%, 11.8%, and 4.8% in cattle, goats, and humans, respectively. Our results indicated that all sheep serum samples were negative on both RBPT and c-ELISA. The seropositive in the 13 camps from Terekeka County was 100.0% (13/13) compared to 50.0% (2/4) seropositive from 4 camps in Juba County. All the variables investigated in the univariate analysis of risk factors in cattle were significantly associated with Brucella seropositivity: sex (OR:4.5, 95% CI: 2.2–8.9, p<0.001), age (OR:6.6, 95% CI: 2.3–19.1, p:<0.001), abortion history (OR:3.1, 95% CI: 1.8–5.2, p:<0.001), retained placenta (OR:2.5, 95% CI: 1.4–4.4, p = 0.001), parity (OR:2.3, 95% CI: 1.1–4.7, p = 0.020), However, in small ruminants, none of the potential risk factors were associated with Brucella seropositivity. In humans, blowing air through a cow’s vagina (OR: 1.4, 95%CI: 0.782–2.434, p = 0.035) was the only variable found to be significantly associated with Brucella seropositivity in the univariate analysis. The forceful blowing of air into a cow’s vagina to induce milk letdown is a common practice among the pastoral communities in South Sudan. The multivariable logistic regression model identified sex, age, and abortion history as statistically significant factors for Brucella seropositivity in cattle. The odds of seropositivity were nearly threefold (OR: 2.8; 95% CI: 1.3–5.8, p = 0.006) higher in cows compared to bulls (male cattle). Cattle over two years old had higher odds of Brucella seropositivity than young animals (OR: 3.5, 95% CI: 1.2–10.3-, p: 0.025). Cows with a history of abortion had higher odds of Brucella seropositivity (OR: 2.8, 95% CI: 1.6–4.7, p = 0.001). CONCLUSIONS : This study reports the occurrence of brucellosis in goats and its absence in sheep in (CES), South Sudan. The present study also shows the occurrence of brucellosis in cattle, goats and people in the pastoral community and recommends for the implementation of the One Health approach and awareness campaigns for effective mitigation of this disease.
Epidemiology of wild animal rabies in Namibia from 2001 to 2019 : implications for controlling the infection in domestic animals
(BioMed Central, 2025-03) Madzingira, Oscar; Hikufe, Emmanuel Hikufe; Byaruhanga, Charles; Lukubwe, Michael Sinvula; Chinyoka, Simbarashe; Mwenda, Evelyn Nanjeke; Muradzikwa, Esther Mariana
BACKGROUND : Rabies is an acute, fatal zoonosis of mammals that is endemic in Namibia. Wild animals have been implicated as reservoirs of the infection around the world. In this retrospective study, passive surveillance data (2001–2019) for wild animal rabies in Namibia were retrieved from the Directorate of Veterinary Services and analysed. The number, spatiotemporal epidemiology, and clinical presentation of rabies cases were assessed and compared among animal species, land use systems and regions. RESULTS : The overall positive rate was 64.8% (1059/1635). Rabies infected 33 out of 52 wild animal species tested. The majority of cases were in Greater Kudu (Tragelaphus strepsiceros) (71.3%, n = 755/1059), followed by the black-backed jackal (Canis mesomelas) (17.1%, 181/1059), eland (Taurotragus oryx) (5.1%, 54/1059), and 30 other wild animal species with low infection rates. Most positive cases (72.8%, 771/1059), and infected wild animal species (n = 26) were from commercial farms. Rabies cases were clustered in the central-western regions of the country (Otjozondjupa, n = 373; Khomas, n = 210; Erongo, n = 123; Omaheke, n = 105; and Kunene, n = 154). Local Moran analysis revealed that the Otjozondjupa region was a significant high-risk cluster of rabies (p = 0.0096). The global Moran’s I analysis by Monte Carlo permutations confirmed significant positive spatial autocorrelation of overall rabies cases from wild animal species in Namibia (Moran’s I = 0.13; p = 0.042). Rabid animals presented the typical clinical signs of rabies. Jackals were responsible for most human and domestic animal bites (80%, 76/95). The number of rabies cases fluctuated over the years, but a clear decline was apparent from 2014 to 2019. The aggregated rabies cases were higher from January to June and lower from July to December. CONCLUSIONS : The results of this study confirm that rabies affects various wild animal species in Namibia, which may act as reservoirs of infection and hinder the control and elimination of dog-mediated rabies. A multi-sector One Health approach towards rabies control anchored on pet vaccination is recommended at Namibia’s human-wildlife-livestock interfaces. Innovative strategies for controlling kudu and jackal rabies are required to reduce incidence in the wild.
Immunogenic profile of a plant-produced nonavalent African horse sickness viral protein 2 (VP2) vaccine in IFNAR-/-mice
(Public Library of Science, 2024-04-16) O’Kennedy, Martha M.; Roth, Robyn; Ebersohn, Karen; Du Plessis, Lissinda H.; Mamputha, Sipho; Rutkowska, Daria A.; Du Preez, Ilse; Verschoor, Jan Adrianus; Lemmer, Yolandy
A safe, highly immunogenic multivalent vaccine to protect against all nine serotypes of African horse sickness virus (AHSV), will revolutionise the AHS vaccine industry in endemic countries and beyond. Plant-produced AHS virus-like particles (VLPs) and soluble viral protein 2 (VP2) vaccine candidates were developed that have the potential to protect against all nine serotypes but can equally well be formulated as mono- and bi-valent formulations for localised outbreaks of specific serotypes. In the first interferon α/β receptor knock-out (IFNAR-/-) mice trial conducted, a nine-serotype (nonavalent) vaccine administered as two pentavalent (5 μg per serotype) vaccines (VLP/VP2 combination or exclusively VP2), were directly compared to the commercially available AHS live attenuated vaccine. In a follow up trial, mice were vaccinated with an adjuvanted nine-serotype multivalent VP2 vaccine in a prime boost strategy and resulted in the desired neutralising antibody titres of 1:320, previously demonstrated to confer protective immunity in IFNAR-/- mice. In addition, the plant-produced VP2 vaccine performed favourably when compared to the commercial vaccine. Here we provide compelling data for a nonavalent VP2-based vaccine candidate, with the VP2 from each serotype being antigenically distinguishable based on LC-MS/MS and ELISA data. This is the first preclinical trial demonstrating the ability of an adjuvanted nonavalent cocktail of soluble, plant-expressed AHS VP2 proteins administered in a prime-boost strategy eliciting high antibody titres against all 9 AHSV serotypes. Furthermore, elevated T helper cells 2 (Th2) and Th1, indicative of humoral and cell-mediated memory T cell immune responses, respectively, were detected in mouse serum collected 14 days after the multivalent prime-boost vaccination. Both Th2 and Th1 may play a role to confer protective immunity. These preclinical immunogenicity studies paved the way to test the safety and protective efficacy of the plant-produced nonavalent VP2 vaccine candidate in the target animals, horses.
Comparing microbiological and molecular diagnostic tools for the surveillance of anthrax
(Public Library of Science, 2024-11-21) Ochai, Sunday Ochonu; Hassim, Ayesha; Dekker, Edgar H.; Magome, Thuto; Lekota, Kgaugelo Edward; Makgabo, Sekgota Marcus; De Klerk-Loris, Lin-Mari; Van Schalkwyk, Louis O.; Kamath, Pauline L.; Turner, Wendy C.; Van Heerden, Henriette
The diagnosis of anthrax, a zoonotic disease caused by Bacillus anthracis can be complicated by detection of closely related species. Conventional diagnosis of anthrax involves microscopy, culture identification of bacterial colonies and molecular detection. Genetic markers used are often virulence gene targets such as B. anthracis protective antigen (pagA, also called BAPA, occurring on plasmid pXO1), lethal factor (lef, on pXO1), capsule encoding capB/C (located on pXO2) as well as chromosomal Ba-1. Combinations of genetic markers using real-time/quantitative polymerase chain reaction (qPCR) are used to confirm B. anthracis from culture but can also be used directly on diagnostic samples to avoid propagation and its associated biorisks and for faster identification. We investigated how the presence of closely related species could complicate anthrax diagnoses with and without culture to standardise the use of genetic markers using qPCR for accurate anthrax diagnosis. Using blood smears from 2012–2020 from wildlife mortalities (n = 1708) in Kruger National Park in South Africa where anthrax is endemic, we contrasted anthrax diagnostic results based on qPCR, microscopy, and culture. From smears, 113/1708 grew bacteria in culture, from which 506 isolates were obtained. Of these isolates, only 24.7% (125 isolates) were positive for B. anthracis based on genetic markers or microscopy. However, among these, merely 4/125 (3.2%) were confirmed B. anthracis isolates (based on morphology, microscopy, and sensitivity testing to penicillin and gamma-phage) from the blood smear, likely due to poor survival of spores on stored smears. This study identified B. cereus sensu lato, which included B. cereus and B. anthracis, Peribacillus spp., and Priestia spp. clusters using gyrB gene in selected bacterial isolates positive for pagA region using BAPA probe. Using qPCR on blood smears, 52.1% (890 samples) tested positive for B. anthracis based on one or a combination of genetic markers which included the 25 positive controls. Notably, the standard lef primer set displayed the lowest specificity and accuracy. The Ba-1+BAPA+lef combination showed 100% specificity, sensitivity, and accuracy. Various marker combinations, such as Ba-1+capB, BAPA+capB, Ba-1+BAPA+capB+lef, and BAPA+lef+capB, all demonstrated 100.0% specificity and 98.7% accuracy, while maintaining a sensitivity of 96.6%. Using Ba-1+BAPA+lef+capB, as well as Ba-1+BAPA+lef with molecular diagnosis accurately detects B. anthracis in the absence of bacterial culture. Systematically combining microscopy and molecular markers holds promise for notably reducing false positives. This significantly enhances the detection and surveillance of diseases like anthrax in southern Africa and beyond and reduces the need for propagation of the bacteria in culture.
Exploring the microbiomes of camel ticks to infer vector competence : insights from tissue-level symbiont-pathogen relationships
(Scientific Reports, 2025-02) Khogali, Rua; Bastos, Armanda D.S.; Getange, Dennis; Bargul, Joel L.; Kalayou, Shewit; Ongeso, Nehemiah; Verhoeven, Joost Theo Petra; Kabii, James; Ngiela, John; Masiga, Daniel; Villinger, Jandouwe
Ticks are blood-feeding ectoparasites that harbor diverse pathogens and endosymbionts. Their microbial communities vary based on tick species, stage, sex, geographical location, surrounding environment, and tissue type. Understanding tick microbiota at the tissue level is crucial for unraveling how microbiomes are distributed in tick tissues and influence pathogen transmission. We used V1-V2 16 S rRNA gene sequencing to analyze tissue-specific bacterial compositions (hemolymph, saliva, salivary glands, and midgut) of Amblyomma gemma, Rhipicephalus pulchellus, Hyalomma dromedarii, and Hyalomma rufipes ticks collected from camels in Marsabit County, northern Kenya. The V1-V2 region of the 16 S rRNA gene effectively differentiated 43 Rickettsia africae and 16 Rickettsia aeschlimannii tick samples from other rickettsial species, as well as Coxiella endosymbionts from Coxiella burnetii. In contrast, the V3-V4 region sequences of these species could not be clearly distinguished. Coxiella endosymbionts were most common in Am. gemma and Rh. pulchellus, while Francisella endosymbionts predominated in Hyalomma ticks; both were primarily localized in the salivary glands. High abundances of Coxiella endosymbionts, as well as Pseudomonas, were associated with the absence or low abundance of Rickettsia pathogens in both Am. gemma and Rh. pulchellus, suggesting competitive interactions between these microbes. Additionally, Proteus mirabilis, an opportunistic pathogen of the urinary tract in humans, was found predominantly in Hyalomma ticks, except for the salivary glands, which were most abundant with Francisella endosymbionts. Furthermore, we detected the Acinetobacter, Pseudomonas, and Corynebacterium genera in all the tick tissues, supporting the hypothesis that these bacteria might circulate between camel blood and ticks. Saliva and hemolymph generally harbored more extracellular bacteria than the salivary glands and midgut. This study provides a new approach to unravel tick-endosymbiont-pathogen interactions by examining the tissue localization of tick-borne pathogens and symbionts in Am. gemma, Rh. pulchellus, Hy. dromedarii, and Hy. rufipes from camels in northern Kenya. Our findings establish a baseline for developing an understanding of the functional capacities of symbionts and for designing symbiont-based control strategies.
A Bayesian latent class estimation of the diagnostic accuracy of clinical examination and laboratory assays to identify bovine ephemeral fever virus infection in South African cattle
(Elsevier, 2025-06) Grobler, Miemie; Fosgate, Geoffrey Theodore; Swanepoel, Robert; Crafford, Jan Ernst; miemie.grobler@up.ac.za
Bovine ephemeral fever (BEF) is an economically important vector-borne viral disease of cattle and water buffalo in Africa, Australia and parts of Asia. The control of BEF is centred around vaccination, and therefore accurate, early identification of disease outbreaks are key to minimize its economic and welfare impact. In Africa, control programs are hampered by limited diagnostic capabilities and poor infrastructure for rapid transportation of diagnostic specimens. The primary objective of this study was to estimate the sensitivity (Se) and specificity (Sp) of four tests, namely clinical examination by a veterinarian, virus isolation and two different conventional PCR assays, to identify an acute bovine ephemeral fever virus (BEFV) infection in diseased, naturally infected South African cattle, without the assumption of a reference standard. Samples and data were collected from cattle with clinical signs suggestive of BEF rather than a random sample of cattle. A case was categorised as clinical examination positive if the examining veterinarian considered acute BEFV-infection as the most likely aetiology. Virus isolation was performed using the buffy coat of heparin blood samples on baby hamster kidney cell cultures, evaluating cytopathic effect and confirming virus morphology by transmission electron microscopy. PCR was performed using two previously published protocols: The Ephemerovirus L-gene PCR (targeting the RNA-dependent RNA polymerase gene) and a BEFV G-gene PCR (targeting the neutralising G1 epitope of the glycoprotein). A single population, four test Bayesian latent class model with conditional dependence between the two PCR assays was implemented. The prevalence of BEFV-infection was high in this study population of clinical suspects at 67 %, (95 % Probability Interval (PI) 52 %; 81 %). Clinical examination provided a reasonable indication of acute BEFV infection (Se of 86 % (PI 77 %; 93 %) and Sp of 67 % (PI 52 %; 82 %)). Virus isolation was the most specific (99 % (PI 97 %; 100 %)), but least sensitive assay (30 % (PI 20 %; 44 %)). Of the two conventional PCRs, the L-gene PCR outperformed the G-gene PCR: The L-gene Se was 64 % (PI 51 %; 76 %) and Sp 96 % (PI 84 %; 100 %) compared to Se of 50 % (PI 38 %; 61 %) and Sp of 89 % (PI 75 %; 98 %) for the G-gene. While the laboratory assays presented excellent positive predictive values within this high disease prevalence population, the poor negative predictive values limit their usefulness to field veterinarians attempting to exclude BEF as diagnosis. Novel pen-side diagnostics should be developed due to the limitations of currently available assays and infrastructure constraints prevalent in Africa.
Phylogeny of multiple genomic regions of infectious laryngotracheitis virus in Turkish poultry flocks
(Elsevier, 2025-05) Aydin, O.; Bayraktar, E.; Tali, H.E.; Ozkan, I.E.; Yilmaz, A.; Umar, S.; Bamac, O.E.; Turan, N.; Konuk, C.; Sadeyen, J.-R.; Chang, P.; Richt, Juergen A.; Iqbal, M.; Yilmaz, H.
Infectious laryngotracheitis (ILT) is an economically significant respiratory tract viral disease affecting poultry worldwide. There is a scarcity of data on the types of ILTV strains circulating in Turkey. This study aimed to determine the frequency and genotypic variations of Turkish ILTV strains. Commercial layer flocks (n = 14) and broiler flocks (n = 105) with a history of respiratory diseases were visited. From each flock, 5 to 10 birds from different age groups were necropsied. Clinical and pathological lesions were recorded, and tracheal tissue samples were collected for further studies. Nucleic acid was extracted from samples and subjected to ILTV detection using PCR assays. Clinical signs of anorexia, lethargy, swollen eyelids, mild to severe conjunctivitis, mucoid to purulent nasal discharge, and a drop in egg production were generally observed among ILTV-infected flocks. Pathological lesions, including conjunctivitis, mucoid to purulent sinusitis, and hemorrhagic tracheitis, were observed during necropsy. Among 119 flocks (14 layers and 105 broiler) analyzed in this study, 17 (17/119, 14.28 %) flocks were found positive for ILTV infection by PCR. Of the 17 ILTV-positive samples, 15 could be sequenced successfully for partial gB, gG, and ICP4 genes. Comparative analysis of partial ICP4 gene nucleotides revealed a unique 18 bp insertion "GCGGTTCTTGCGGTTGTT" among ILTV strains. Two nucleotide substitutions were observed in gB gene sequences at positions 5 (T to C) and 488 (A to G), resulting in amino acid substitutions at positions 2 (I to T) and 163 (K to R). Phylogenetic analysis of the gB gene revealed a close clustering (Cluster I) between ILTV strains from this study and those reported from China, Australia, and the USA. Phylogenetic analysis of gG gene sequences showed a close relation to ILTV strains from Russia, China, Canada, the USA, and Italy. No recombination events were observed among the partial sequences of ILTV genes analyzed in this study. Findings of this study show that ILTV infections are frequent in Turkish poultry flocks and contribute to our understanding of the genomic variations in gB, gG and ICP4 genes of ILTV which might help to mitigate ILTV infections in Turkey.
Bacterial blood microbiome of Mastomys rodents : implications for disease spill-over at the animal-human interface within the Bushbuckridge-East community, South Africa
(Frontiers Media, 2025-02) Kolo, Agatha Onyemowo; Brayton, Kelly A.; Collins, Nicola E.; Bastos, Armanda D.S.; Matthee, Sonja; Gall, Cory A.; Wentzel, Jeanette Maria; Neves, L.C.B.G.D. (Luís); Oosthuizen, Marinda C.
The Bushbuckridge-East community in Mpumalanga Province, South Africa is bordered by nature reserves, including the Manyeleti Game Reserve. Murid rodents are prevalent in both Manyeleti and communal rangelands adjoining the community households. Although rodents are reservoir hosts for a broad range of viral, bacterial and parasitic pathogens, the rodent microbial diversity and transmission of zoonotic agents to humans in the community is understudied. In this study we investigated bacterial diversity in wild and commensal rodents sampled from different habitats. The 16S rRNA gene was amplified from DNA extracted from the blood of 24 wild Mastomys and one Steatomys sp. and subjected to PacBio circular consensus sequencing. As Bartonella species were dominant in the blood microbiome, gltA gene characterization was performed to delineate species. Rodents sampled from peri-urban and communal rangelands had higher proportions of Bartonella spp. [Hlalakahle (77.7%), Gottenburg (47.8%), Tlhavekisa (83.8%)] compared to those from the protected habitat (43.8%). Ehrlichia spp., Anaplasma spp., and Coxiella burnetii were detected at <1% of the sequence reads. Conventional PCR and sequencing validated the detection of Bartonella spp. with the first confirmation of Bartonella mastomydis infection in Mastomys in South Africa. Additionally, 317 mites, 90 fleas, 10 ticks and eight lice were collected from the rodents, providing evidence of possible vectors of the organisms detected. The detection of zoonotic agents in rodents in Bushbuckridge-East community, together with prior serological confirmation of Bartonella and Coxiella in non-malarial acute febrile patients from this community, highlights the possible risks that commensal rodents pose to human health.

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