Research Articles (Veterinary Tropical Diseases)

Permanent URI for this collectionhttp://hdl.handle.net/2263/1710

News

For inquiries regarding this collection or items in the collection, please contact Tertia Coetsee Tel.: +27 12 420 8580

Browse

Now showing 1 - 20 of 1261

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.
Phylogenomics of Brucella abortus isolated from African buffalo in Kruger National Park : new perspectives on wildlife-cattle disease dynamics
(Elsevier, 2025-05) Cossu, Carlo Andrea; Garofolo, Giuliano; Janowicz, Anna; De Massis, Fabrizio; Wentzel, Jeanette Maria; Ledwaba, Maphuti Betty; Sabeta, Claude; De Klerk, Lin-Mari; Godfroid, Jacques; Vergnaud, Gilles; Van Heerden, Henriette; ca.cossu@tuks.co.za
In South Africa, Brucella abortus biovar 1 is the primary cause of bovine brucellosis, significantly impacting cattle production and trade. Serological studies have revealed brucellosis in African wildlife, complicating control efforts due to limited epidemiological data. In 1977, B. abortus biovar 1 was isolated from an African buffalo fetus in Kruger National Park (KNP), raising speculation that buffalo may serve as reservoir hosts. This study investigated Brucella spp. in free-ranging buffalo in KNP using serological, molecular, and bacteriological methods. Brucella abortus bv 1 was isolated from lymph nodes and spleens of three sub-adult buffalo in 2022, marking the first documented recurrence in 50 years. Phylogenomic analyses revealed connections between buffalo isolates and cattle strains from South Africa and South America, suggesting spillover and shared origins from Europe. Further genomic and epidemiological surveillance is required to clarify the role of buffalo as reservoir hosts for brucellosis.
Preslaughter practices, pork physicochemical attributes and fatty acid profiles of pigs raised and slaughtered on smallholder urban farms in the Cape Metropole, South Africa
(Elsevier, 2025-06) Mathobela, Rebecca M.; Chikwanha, Obert C.; Katiyatiya, Chenaimoyo L.F.; Semwogerere, Farouk; Molotsi, Annelin H.; Marufu, Munyaradzi Christopher; Strydom, Phillip E.; Mapiye, Cletos
Pre-slaughter practices, pork physicochemical quality, and fatty acid (FA) composition of 36 Landrace barrows aged six months, sourced from five smallholder urban farms (SUFs) in low-income, high-density suburbs and one commercial abattoir in Cape Metropole District, South Africa were evaluated. Pigs on SUFs were fed three diets: (1) kitchen-bakery-vegetable waste-based, (2) bakery-dairy waste-based, or (3) homemade grain-based, while those on a large-scale farm were fed a commercial diet. Pigs on SUFs were either stunned mechanically or not stunned before slaughter. The SUFs either practiced throat or cervical spine sticking during slaughter. Carcasses from pigs fed the homemade grain-based diet had higher (P ≤ 0.05) weights, ash subcutaneous and intramuscular fat (IMF) values than those fed the other diets. The homemade grain-based diet, throat sticking treatment produced pork with the highest pH45 followed by the bakery-dairy waste-based diet, throat sticking and kitchen-bakery-vegetable waste-based diet, cervical spine treatments (P ≤ 0.05). Pigs fed a commercial diet and slaughtered by throat sticking produced pork with the lower (P ≤ 0.05) values for pH24, colour coordinates (L*, a*, b*, H° and C°) and the higher (P ≤ 0.05) carcass temperature and shear force values relative to the other treatments. Pork from pigs fed the homemade grain-based diets had higher (P ≤ 0.05) contents of total FA, total PUFA, individual and total n-6 PUFA than pork from pigs fed the other diets. Pig carcasses stunned with a gun had higher (P ≤ 0.05) pH45, pH24 and shear force values than those not stunned. The homemade grain-based diet improved carcass attributes and fatty acid profiles of pigs raised and slaughtered on SUFs, stunning enhanced pork physical quality attributes while the kitchen-bakery-vegetable waste-based diet, cervical spine sticking treatment produced less desirable pork physical attributes.
Anti-phenolic glycolipid antibodies in Mycobacterium bovis infected cattle
(Elsevier, 2025-06) Zhou, Zijie; Van Hooij, Anouk; Van Dijk, J. Hessel M.; Musch, Nina; Pierneef, Louise; Khalid, Hamza; Franken, Kees; Holder, Thomas; Watt, Neil; Michel, Anita Luise; Codee, Jeroen D.C.; Vordermeier, Martin; Corstjens, Paul L.A.M.; Van der Heijden, Elisabeth M.D.L.; Hope, Jayne C.; Geluk, Annemieke
Mycobacterium bovis, the causative agent of bovine tuberculosis (bTB), causes significant financial losses in the agricultural industry. Additionally, M. bovis transmission from animals to humans can result in zoonotic TB, especially in low- and middle-income countries (LMICs), highlighting the need to enhance One Health surveillance to mitigate this threat. Antibodies directed against a major mycobacterial cell wall component of M. leprae, phenolic glycolipid-I (PGL-I), have shown excellent performance in identifying M. leprae infection in humans and animals. In this study, we therefore investigated whether antibodies against M. bovis PGL similarly represent a useful biomarker for M. bovis infection in cattle. Comparing sera from naturally M. bovis-infected and the single intradermal comparative cervical tuberculin test (SICCT)-negative cattle, we assessed the potential of M. bovis PGL antibodies to identify this mycobacterial infection. Our results show that serum levels of anti-M. bovis PGL IgG and -IgM in M. bovis-infected cattle were significantly higher than in the SICCT-negative cattle. The sensitivity for anti-M. bovis PGL IgM in infected animals was, however, moderate (44.9 %) and the false-positive rate was 6.3 % in SICCT-negative cattle. Notably, vaccination with BCG- or heat-killed M. bovis did not affect serum levels of anti-M. bovis PGL IgM in cattle. Moreover, none of the 57 anti-M. bovis PGL-seropositive cattle tested positive in the anti-M. leprae PGL-I assay. This study shows for the first time that anti M. bovis PGL antibodies can be detected in infected cattle: anti-M. bovis PGL IgM is a highly specific, but moderately sensitive biomarker for M. bovis infection in cattle, showing potential for differentiate infected from vaccinated animals (DIVA). It could be a valuable component in a multi-biomarker approach for diagnosing bTB.
Are there benefits of culture-based detection of over histopathology?
(AOSIS, 2025-02) Hlokwe, Motlatso T.; Masina, Nomawethu Shelly; Letsoko, Boitumelo; Davey, Sewellyn C.; Michel, Anita Luise
Paratuberculosis (Johne’s disease) has devastating outcomes on ruminant health and impacts on national and international trade. The current work assessed the diagnostic value of the VersaTREK automated liquid culture system in isolating Mycobacterium avium subspecies paratuberculosis (MAP) from faecal and intestinal tissue samples from ovine under South African conditions and compared it with the current method of choice, histopathological examination. Intestinal tissue and faecal samples from 111 sheep (including complete set from 104 slaughter sheep from flocks with a history of MAP infection as well as incomplete sample sets from 7 sheep) were analysed using the liquid culture method. One set of tissues was subjected to histopathological examination. Deoxyribonucleic acid (DNA) extracted from culture isolates was subjected to polymerase chain reaction (PCR) amplification using primers that target the IS900 regions of the MAP for species verification. Overall, the VersaTREK automated liquid culture in combination with IS900 PCR showed a comparable level of detection in tissues (12.6%) as histopathology (13.5%), but the detection rate for faecal samples was lower than for tissues (10.8%). A combination of histopathology and faecal culture increased the detection rate from 13.5% (n = 14/104) and 9.6% (n = 10/104), respectively, to 15.4% (n = 16/104). CONTRIBUTION : Our findings highlight the diagnostic utility of the VersaTREK automated liquid culture system in detecting MAP in ovine samples collected both ante and postmortem. However, an inhibitory effect on the MAP isolation rate observed when the antibiotic cocktail was added to the culture medium warrants further investigation. The outcome of the study is beneficial in guiding the strategic planning of the nationwide control programme.
Inequities underlie the alarming resurgence of Tuberculosis as the world's top cause of death from an infectious disease - breaking the silence and addressing the underlying root causes
(Elsevier, 2025-03) Zumla, Alimuddin; Sahu, Suvanand; Ditiu, Lucica; Singh, Urvasha; Park, Young-Joon; Yeboah-Manu, Dorothy; Osei-Wusu, Stephen; Asogun, Danny; Nyasulu, Peter; Tembo, Africa John; Kapata, Nathan; Tembo, John; Alyaqoubi, Fatma; Al Maani, Amal; Blumberg, Lucille Hellen; Zumla, Adam; Ahmed, Rizwan; Go, Unyeong; Hui, David; Goletti, Delia; Petersen, Eskild
No abstract available.
Prevalence of methicillin-resistant Staphylococcus aureus in livestock production system of Nigeria : a systematic review
(Istanbul University, 2025-01) Gaddafi, Mohammed Sani; Yakubu, Yusuf; Bello, Muhammad Bashir; Lawal, Habiba; Bitrus, Asinamai Athliamai; Musawa, Ibrahim Aliyu; Fasina, Folorunso Oludayo
Recently, methicillin-resistant Staphylococcus aureus (MRSA) has been identified as a growing concern in livestock. Animals can serve as reservoirs for MRSA, and the bacteria can be transmitted to humans who are in close contact with animals colonized by MRSA. This study evaluated the prevalence, potential source, and vehicle in the emergence and transmission of livestock-associated MRSA in Nigeria’s livestock production systems over the past decade. A systematic search was conducted on Web of Science, PubMed, Google Scholar, and Scopus databases to identify relevant studies published between 2012 and 2022. Standardized keywords were used. 28 eligible articles were included in the review, and our systematic review protocol was published in Prospero (Registration number: CRD42023431777). The occurrence of MRSA varied across the studies analyzed, ranging from 0% to 53.9%. Specifically, in poultry, the prevalence ranged from 7.9% to 37.5%; in cattle, from 3.21% to 29%; in pigs, from 0% to 53.9%; and in sheep and goats, from 4.4% to 25%. Among livestock farm/abattoir workers, the prevalence of MRSA ranged from 3.1% to 71.4%. The MRSA isolates from Nigeria’s livestock production systems displayed pathogenic potential with various S. aureus protein A (spa) types and clonal complexes (CC) as determined by Based Upon Repeat Pattern (BURP) analysis. These isolates carried genes associated with virulence factors such as enterotoxins, exfoliative toxins, and Panton-Valentine Leukocidin (PVL). One reviewed study documented the identification of the characteristic livestock-associated MRSA CC398 using Multilocus Sequence Typing (MLST) analysis. The livestock production system serves as a potential source and vehicle for the emergence and transmission of MRSA in Nigeria. To effectively prevent and control these infections, continuous monitoring using the “One Health” approach is recommended.
Molecular characterization of virulence and resistance genes in Salmonella strains isolated from chickens sold at the informal chicken market in Gauteng Province, South Africa
(Wiley, 2024-04) Mokgophi, Thelma M.; Gcebe, Nomakorinte; Fasina, Folorunso Oludayo; Adesiyun, Abiodun Adewale
This cross-sectional study determined the occurrence of virulence and antimicrobial resistance genes in Salmonella strains recovered from chicken obtained from informal markets in Gauteng province, South Africa. The study also assessed the relationship between these characteristics, the source, the type of samples, and the serotypes of Salmonella isolates. A total of 151 samples (cloacal swabs, chicken carcasses, and carcass drips) were randomly collected from 47 informal market outlets in six townships in Gauteng province. Salmonella spp. was isolated and identified based on ISO 6579:2002 methods and confirmed by polymerase chain reaction (PCR) targeting invA gene fragment. Conventional PCR was used to detect 12 virulence and 18 antimicrobial resistance (AMR) genes in Salmonella spp. The most frequently detected virulence genes were invA (100%), shdA (91%), mgtB (87.7%), and sopE (81%), but considerably low for spvC (2.2%), sefC (1.5%), and pefC (0.4%). The differences in detection frequency were statistically significant (p < 0.05). Tetracycline-resistant genes tetA (34.7%) and tetB (16%) were the most frequently detected, while Betalactam- resistant genes blaTEM (0.4%), blaCMY-2 (0.4%) and quinolones resistant gene qnrS (0.4%) were detected in low frequency (p < 0.05). The locations of the outlets and the types of samples were significantly associated with detecting some virulence and AMR genes. Significant but moderately to substantial positive correlations were observed for qnrS, sul2; shdA, and mgtB genes. The pipA and spiC were, however, substantially negatively correlated. Our findings show that detecting these virulence and AMR genes in Salmonella isolates serves as a potential health hazard to the public, environment, and poultry farming in Gauteng, South Africa.

Browse

Recent Submissions