A comparative study of the minimum inhibitory and mutant prevention concentrations of florfenicol and oxytetracycline for animal isolates of Pasteurella multocida and Salmonella Typhimurium

This study was undertaken to compare the MIC (minimum inhibitory concentration) and MPC (mutant prevention concentration) values for oxytetracycline and florfenicol against strains of Pasteurella multocida isolated from cattle and pigs, and for enrofloxacin against strains of Salmonella Typhimurium isolated from horses. Isolates of P. multocida from cattle and pigs, and S. Typhimurium from horses were obtained from specimens or isolates from contributing laboratories. All the equine isolates and 50% of the cattle and pig isolates were from clinically sick animals. All isolates were tested in duplicate with both the MIC and the MPC methods. The MIC method used was the standardized microdilution method performed in microtitre plates. The MPC method used was according to the method described by Blondeau. This method was modified, to make use of smaller plates and lower volumes of antimicrobials, but retaining a final bacterial concentration of 109 colony-forming units per ml. The antimicrobials were dissolved as described in the certificates of analyses. Enrofloxacin and oxytetracycline were dissolved in water, and florfenicol was dissolved in alcohol. For the MPC method, an additional control was added to one quadrant of a four-quadrant 90mm plate/petri dish. The antimicrobials were tested as individual antimicrobials and not as combinations. Both the MIC and MPC methods included ATCC (American Type Culture Collection) strains as control organisms and were evaluated according to the guidelines of the CLSI (Clinical and Laboratory Standards Institute). The MIC50 values for enrofloxacin against Salmonella Typhimurium isolates from horses was 0.25 ìg/ml and the MPC50 values 0.5 ìg/ml. A comparative reference range was not available as enrofloxacin is not registered in South Africa for use in horses, and is used extra-labelly. The results for florfenicol against P. multocida yielded an MIC50 value of 0.5 ìg/ml and an MPC50 value of 125, is an effective parameter for treatment of Gram-negative bacteria. The corresponding results for oxytetracycline were above the MIC value but fell within the mutant selection window. The results point to the fact that the use of oxytetracycline against P. multocida may not be effective in preventing the appearance of first step mutant strains when used at current recommended dosages. The PK/PD data, using AUC/MIC, yielded a value of 56. Some of the isolates (55.17%) had an MPC value of 16 ìg/ml. Whereas the MIC method is used routinely in diagnostic laboratories, the MPC method can be employed to generate data that can be applied where antimicrobial treatment of certain bacteria is problematic and standard treatment may lead to the development of resistance. Data obtained from such studies will enable manufacturers of antimicrobial drugs to adapt antimicrobial therapy where practical and feasible to prevent the development of first step mutants.Dissertation (MSc)--University of Pretoria, 2012.Veterinary Tropical Diseasesunrestricte

Die voorkoms van antimikrobiese stowwe in die vleis van uitskot melkkoeie in die Vrystaatstreek en die meegaande kennisvlak van die produsent en verbruikers

Thesis (M. Tech. ) - Central University of Technology, Free State, 2006Antibiotics have been used on animals since the Second World War for therapeutic purposes. The risks associated with the use of antibiotics in food animals are enormous, due to the possibility of resistance of organisms caused by the usage of low levels of antibiotics. The goals of this study were to determine the prevalence of antibiotic residues in C grade milk cows, and to determine the practices and knowledge of producers regarding the use of antibiotics as well as the knowledge and habits of consumers. In the study the presence of antibiotic residues was tested by means of microbiological inhibition testing. Fifteen percent of all tested samples tested positive for the presence of antibiotic residues. Eleven samples that tested positive on the microbiological inhibition test were sent to the Onderstepoort Veterinary Institute for confirmation. The knowledge of the consumer as well as that of the producer was tested by means of a questionnaire and then processed statistically. Producers were, in general, fairly ignorant regarding the withdrawal period of antibiotic residues. Age and the combination of age and reproduction were the common reasons for the selling of milk cows. Both the sampling and the questionnaires proved that the presence of antibiotic residues is higher than that stated in literature. The selling of the animals was mostly by auction or directly to the abattoirs. Consumer practices regarding the antibiotic residues were mostly in order, although consumers did not have knowledge regarding antibiotic residues. High temperatures, for example in the frying or grilling of meat, will reduce the presence of antibiotic residues because these effects have an influence on the presence of antibiotic residues (Rose et al., 1995). Almost 75% of consumers describe antibiotics in a positive manner. Milk and meat are regarded as posing the greatest risk for the origin of antibiotic residues. A lack of general knowledge regarding antibiotic residues was noteworthy, especially from the consumers of Thaba ’Nchu and Heidedal. The wrong usage of antibiotics by medical practitioners and consumers will certainly have consequences. Most of the consumers (112/227 respondents) indicated that they always completed a course of antibiotics. Forty-nine respondents indicated that they had already used antibiotics and that the therapy was unsuccessful. Antibiotic residues are still present so the risk to the consumer is still viable. Improved sampling and monitoring at abattoirs both for local and export abattoirs is necessary. The “farm to fork” concept and financial incentives by way of subsidies for residue-free products is a positive step. South African consumers are not quality conscious and further studies are necessary to improve the quality and safety of meat

Comparing the minimum inhibitory and mutant prevention concentrations of selected antibiotics against animal isolates of Pasteurella multocida and Salmonella typhimurium

This article forms part of the published thesis of J.M.W. submitted in partial fulfilment of the requirements for the degree of Magister Scientiae (Veterinary Tropical Diseases) in the Department of Veterinary Tropical Diseases, Faculty of Veterinary Science, University of Pretoria, South Africa, entitled ‘A comparative study of the minimum inhibitory and mutant prevention concentrations of florfenicol and oxytetracycline for animal isolates of Pasteurella multocida and Salmonella Typhimurium’. Supervisor: M.v.V., 2012. Refer to link: https://repository.up.ac.za/handle/ 2263/26219.DATA AVAILABILITY : The raw data is available on the University of Pretoria repository as part of the M. thesis at https://repository. up.ac.za/handle/2263/26219.Historically, the use of antibiotics was not well regulated in veterinary medicine. The emergence of antibiotic resistance (ABR) in pathogenic bacteria in human and veterinary medicine has driven the need for greater antibiotic stewardship. The preservation of certain antibiotic classes for use exclusively in humans, especially in cases of multidrug resistance, has highlighted the need for veterinarians to reduce its use and redefine dosage regimens of antibiotics to ensure efficacy and guard against the development of ABR pathogens. The minimum inhibitory concentration (MIC), the lowest concentration of an antibiotic drug that will prevent the growth of a bacterium, is recognised as a method to assist in antibiotic dosage determination. Minimum inhibitory concentrations sometimes fail to deal with first-step mutants in bacterial populations; therefore dosing regimens based solely on MIC can lead to the development of ABR. The mutant prevention concentration (MPC) is the minimum inhibitory antibiotic concentration of the most resistant first-step mutant. Mutant prevention concentration determination as a complementary and sometimes preferable alternative to MIC determination for veterinarians when managing bacterial pathogens. The results of this study focused on livestock pathogens and antibiotics used to treat them, which had a MIC value of 0.25 μg/mL for enrofloxacin against all 27 isolates of Salmonella typhimurium. The MPC values were 0.50 μg/mL, with the exception of five isolates that had MPC values of 4.00 μg/mL. The MPC test yielded 65.52% (18 isolates) Salmonella isolates with florfenicol MICs in the sensitive range, while 11 isolates were in the resistant range. Seventeen isolates (58.62%) of Pasteurella multocida had MIC values in the susceptible range and 41.38% (12 isolates) had an intermediate MIC value. Mutant prevention concentration determinations as done in this study is effective for the antibiotic treatment of bacterial infections and minimising the development of resistance. The MPC method can be used to better control to prevent the development of antibiotic drug resistance used in animals.http://www.ojvr.orgam2023Production Animal StudiesVeterinary Tropical Disease

The first report of Escherichia fergusonii isolated from non-human primates, in Africa

The aim of this study was to determine the resistance phenotypes of selected enteric bacteria isolated from nonhuman primates at a wildlife-human interface. Bacterial isolates from faecal samples of non-human primates at two wildlife rehabilitation centres in South Africa were screened for the presence of Escherichia coli. The biochemical characterisation of E. coli and E. coli-like bacteria revealed both adonitol positive and sorbitol negative strains – a unique characteristic of Escherichia fergusonii and Escherichia coli K99. Further tests were carried out to identify the isolates, namely growth on Simmons citrate agar supplemented with 2% adonitol and biochemical tests based on their ability to ferment cellobiose and D-arabitol. Antimicrobial sensitivity was determined with microbroth dilution tests employing microtitre plates with 21 different antimicrobial drugs. Molecular characterisation was done with a duplex polymerase chain reaction (PCR) assay that targeted the yliE and EFER_1569 genes. E. fergusonii strains were confirmed by the presence of a 233 bp segment of the yliE gene and a 432 bp segment of the EFER_1569 gene. Twenty-three E. coli-like bacteria were confirmed as E. fergusonii based on the confirmatory tests and they were in 100% agreement. Approximately 87% of them were resistant to polymyxins B and E (colistin) as well as the carbapenem group with occasional resistance to amikacin. This is the first reported isolation and identification of E. fergusonii strains in non-human primates. The findings point to E. fergusonii as a possible emerging pathogen of zoonotic importance.https://www.elsevier.com/locate/onehltam2018Veterinary Tropical Disease

Mitochondrial genome sequence comparisons indicate that the elephant louse Haematomyzus elephantis (Piaget, 1869) contains cryptic species

DATA AVAILABILITY STATEMENT : Annotated mitochondrial genome sequences of the African savanna elephant lice produced in the current study are available in GenBank (accession numbers OQ834926-OQ834934; https://www.ncbi.nlm.nih.gov/genbank/); raw Illumina sequence data are available in the NCBI Sequence Read Archive (SRA) database (BioProject accession number PRJNA1021748). Genomic sequence reads of an Asian elephant louse (SRR5308122) and transcriptomic sequence reads of an Asian elephant louse (SRR2051491) are available in the SRA database (https://www.ncbi.nlm.nih.gov/sra).SUPPLEMENTARY MATERIAL S1. PCR primers used to amplify the mitochondrial genes or minichromosomes of the African savanna elephant louse.SUPPLEMENTARY MATERIAL S2. Mitochondrial cox1 gene sequence divergence between closely related congeneric species of parasitic lice.SUPPLEMENTARY MATERIAL S3. The fully sequenced S2-R-nad4L-M-G-nad3 mitochondrial minichromosome of African savanna elephant louse (RS460). trnG, trnM, trnR and trnS2 are tRNA genes for amino acids glycine, methionine, arginine and serine respectively. nad3 and nad4L are for NADH dehydrogenase subunits 3 and 4L. SKnad4LFO2 and SKnad4LRO2 are the primer pair that amplifies the entire S2-R-nad4L-M-G-nad3 minichromosome.SUPPLEMENTARY MATERIAL S4. Mitochondrial gene sequence divergence between African (RS460) and Asian elephant lice (B1567, SRR5308122.SUPPLEMENTARY MATERIAL S5. Mitochondrial gene sequence divergence among Asian elephant lice (B1567, SRR5308122 and SRR2051491).SUPPLEMENTARY MATERIAL S6. Mitochondrial cox1 gene and genome sequence divergence between African savanna elephant (Loxodonta africana, GenBank accession number NC_000934) and Asian elephant (Elephas maximus, NC_005129).The parvorder Rhynchopthirina contains three currently recognised species of lice that parasitize elephants (both African savanna elephant Loxodonta africana and Asian elephant Elephas maximus), desert warthogs (Phacochoerus aethiopicus) and Red River hogs (Potamochoerus porcus), respectively. The Asian elephant lice and the African savanna elephant lice are currently treated as the same species, Haematomyzus elephantis (Piaget, 1869), based on morphology despite the fact that their hosts diverged 8.4 million years ago. In the current study, we sequenced 23 mitochondrial (mt) genes of African savanna elephant lice collected in South Africa and analysed the sequence divergence between African savanna elephant lice and previously sequenced Asian elephant lice. Sequence comparisons revealed >23% divergence for the 23 mt genes as a whole and ~17% divergence for cox1 gene between African savanna and Asian elephant lice, which were far higher than the divergence expected within a species. Furthermore, the mt gene sequence divergences between these lice are 3.76–4.6 times higher than that between their hosts, the African savanna and Asian elephants, which are expected for the co-divergence and co-evolution between lice and their elephant hosts. We conclude that (1) H. elephantis (Piaget, 1869) contains cryptic species and (2) African savanna and Asian elephant lice are different species genetically that may have co-diverged and co-evolved with their hosts.University of the Sunshine Coast.Open access publishing facilitated by University of the Sunshine Coast, as part of the Wiley - University of the Sunshine Coast agreement via the Council of Australian University Librarians.http://wileyonlinelibrary.com/journal/mvehj2024Centre for Veterinary Wildlife StudiesVeterinary Tropical DiseasesSDG-03:Good heatlh and well-bein

Amblyomma hebraeum is the predominant tick species on goats in the Mnisi Community Area of Mpumalanga Province South Africa and is co-infected with Ehrlichia ruminantium and Rickettsia africae

BACKGROUND : In sub-Saharan Africa, Amblyomma ticks are vectors of heartwater disease in domestic ruminants, caused by the rickettsial pathogen Ehrlichia ruminantium. Immature tick stages often bite humans, whereby they act as vectors of tick-bite fever caused by Rickettsia africae. Moreover, Amblyomma ticks cause damage to livestock due to their feeding behaviour. In South Africa, we studied the abundance of Amblyomma hebraeum ticks on goats of emerging farmers in Mpumalanga Province. A selected number of A. hebraeum nymphs and adult ticks was tested for co-infection with E. ruminantium and R. africae. METHODS : A total of 630 indigenous goats, belonging to farmers in the Mnisi Community area, were examined for ticks in 2013 and 2014. All ticks were identified, and a selected number was tested by PCR with reverse line blot hybridisation. RESULTS : In total, 13,132 ticks were collected from goats distributed over 17 different households. Amblyomma hebraeum was the predominant species, followed by R. microplus. Rhipicephalus appendiculatus, R. simus and R. zambeziensis were also identified. Amblyomma hebraeum was present throughout the year, with peak activity of adults in summer (November) and nymphs in winter (July). The ratio between adults and nymphs ranged from 1:2.7 in summer to 1:55.1 in winter. The mean prevalence of infection for E. ruminantium by PCR/RLB in adult ticks was 17.4% (31/178), whereas 15.7% (28/178) were infected with R. africae. In pooled nymphs, 28.4% were infected with E. ruminantium and 38.8% carried R. africae infection. Co-infections of E. ruminantium and R. africae in adult and pooled nymphal ticks were 3.9% (7/178) and 10% (14.9), respectively. Lameness of goats due to predilection of ticks for the interdigital space of their feet was observed in 89% of the households. CONCLUSIONS : Goats act as important alternative hosts for cattle ticks, which underscored the necessity to include goats in control programs. It is suggested to use acaricide-impregnated leg-bands as a sustainable method to kill ticks and prevent lameness in goats. The challenge of goats by considerable numbers of E. ruminantium-infected ticks is a major obstacle for upgrading the indigenous goat breeds. Humans may be at risk to contract tick-bite fever in this area.The Faculty of Veterinary Medicine of Utrecht University and the Faculty of Veterinary Science of the University of Pretoria.http://www.parasitesandvectors.comhj2020Veterinary Tropical Disease

Occurrence and molecular prevalence of Anaplasmataceae , Rickettsiaceae and Coxiellaceae in African wildlife : a systematic review and meta-analysis

SUPPLEMENTARY MATERIAL : TABLE S1: PRISMA statement checklist; TABLE S2: PRISMA checklist for abstracts; TABLE S3: additional checklist for systematic reviews and meta-analyses retrieved from Migliavaca et al., 2020; TABLE S4: critical appraisal of included studies; TABLE S5: detailed summary of Anaplasmataceae, Rickettsiaceae and Coxiellaceae detected in African wildlife stratified by country and detection method; TABLE S6: results of the analysis of publication bias; TABLE S7: List of papers excluded during full-text examination and relevant exclusion criteriaINTRODUCTION : Tick-borne pathogens (TBPs) constitute an emerging threat to public and animal health especially in the African continent, where land-use change, and wildlife loss are creating new opportunities for disease transmission. A review of TBPs with a focus on ticks determined the epidemiology of Rhipicephalus ticks in heartwater and the affinity of each Rickettsia species for different tick genera. We conducted a systematic review and meta-analysis to collect, map and estimate the molecular prevalence of Anaplasmataceae, Rickettsiaceae and Coxiellaceae in African wildlife. MATERIALS AND METHODS : Relevant scientific articles were retrieved from five databases: PubMed, ScienceDirect, Scopus, Ovid and OAIster. Publications were selected according to pre-determined exclusion criteria and evaluated for risk of bias using the appraisal tool for cross-sectional studies (AXIS). We conducted an initial descriptive analysis followed by a meta-analysis to estimate the molecular prevalence of each pathogen. Subgroup analysis and meta-regression models were employed to unravel associations with disease determinants. Finally, the quality of evidence of every estimate was finally assessed. RESULTS : Out of 577 retrieved papers, a total of 41 papers were included in the qualitative analysis and 27 in the meta-analysis. We retrieved 21 Anaplasmataceae species, six Rickettsiaceae species and Coxiella burnetii. Meta-analysis was performed for a total of 11 target pathogens. Anaplasma marginale, Ehrlichia ruminantium and Anaplasma centrale were the most prevalent in African bovids (13.9 %, CI: 0–52.4 %; 20.9 %, CI: 4.1–46.2 %; 13.9 %, CI: 0–68.7 %, respectively). Estimated TBPs prevalences were further stratified per animal order, family, species and sampling country. DISCUSSION : We discussed the presence of a sylvatic cycle for A. marginale and E. ruminantium in wild African bovids, the need to investigate A. phagocytophilum in African rodents and non-human primates as well as E. canis in the tissues of wild carnivores, and a lack of data and characterization of Rickettsia species and C. burnetii. CONCLUSION : Given the lack of epidemiological data on wildlife diseases, the current work can serve as a starting point for future epidemiological and/or experimental studies.http://www.elsevier.com/locate/prevetmedhj2024Centre for Veterinary Wildlife StudiesProduction Animal StudiesVeterinary Tropical DiseasesSDG-03:Good heatlh and well-beingSDG-15:Life on lan

Rabies vaccination of 6‐week‐old puppies born to immunized mothers: a randomized controlled trial in a high‐mortality population of owned, free‐roaming dogs

To achieve global elimination of human rabies from dogs by 2030, evidence-based strategies for effective dog vaccination are needed. Current guidelines recommend inclusion of dogs younger than 3 months in mass rabies vaccination campaigns, although available vaccines are only recommended for use by manufacturers in older dogs, ostensibly due to concerns over interference of maternally-acquired immunity with immune response to the vaccine. Adverse effects of vaccination in this age group of dogs have also not been adequately assessed under field conditions. In a single-site, owner-blinded, randomized, placebo-controlled trial in puppies born to mothers vaccinated within the previous 18 months in a high-mortality population of owned, free-roaming dogs in South Africa, we assessed immunogenicity and effect on survival to all causes of mortality of a single dose of rabies vaccine administered at 6 weeks of age. We found that puppies did not have appreciable levels of maternally-derived antibodies at 6 weeks of age (geometric mean titer 0.065 IU/mL, 95% CI 0.061–0.069; n = 346), and that 88% (95% CI 80.7–93.3) of puppies vaccinated at 6 weeks had titers ≥0.5 IU/mL 21 days later (n = 117). Although the average effect of vaccination on survival was not statistically significant (hazard ratio [HR] 1.35, 95% CI 0.83–2.18), this effect was modified by sex (p = 0.02), with the HR in females 3.09 (95% CI 1.24–7.69) and the HR in males 0.79 (95% CI 0.41–1.53). We speculate that this effect is related to the observed survival advantage that females had over males in the unvaccinated group (HR 0.27; 95% CI 0.11–0.70), with vaccination eroding this advantage through as-yet-unknown mechanisms.Supplementary Materials: Table S1. Results of sensitivity analysis for survival analysis (6 to 13 weeks of age), considering subjects reported as lost or stolen by owners as dead (n = 22); Table S2. Results of sensitivity analysis for survival analysis (6 to 13 weeks of age), censoring subjects that reportedly died from accidents (n = 5).http://www.mdpi.com/journal/tropicalmedhj2021Companion Animal Clinical StudiesProduction Animal StudiesVeterinary Tropical Disease

Phenotypic and genotypic characterization of acaricide resistance in Rhipicephalus microplus field isolates from South Africa and Brazil

AVAILABILITY OF DATA AND MATERIALS : The datasets generated and/or analysed during the current study are available from the corresponding author on reasonable request.Rhipicephalus (Boophilus) microplus is one of the most successful ticks infesting cattle around the world. This highly-invasive species transmits cattle parasites that cause cattle fever leading to a high socio-economic burden. Tick eradication programs have often failed, due to the development of acaricide resistance. Here we characterize acaricide resistance in a large number of tick isolates from regions in South Africa (KwaZulu Natal, Mpumalanga, Western & Eastern Cape provinces) and two Brazilian regions. By means of Larval Packet Tests (LPT's) acaricide resistance was evaluated against five commonly used acaricides (chlorfenvinphos, fipronil, deltamethrin, amitraz, and ivermectin). Furthermore, the coding region containing the knock down resistance (kdr) mutation, known to result in pyrethroid resistance, was sequenced. Resistance to at least one acaricide class was reported in each of the five regions, and a high proportion of tick isolates exhibited multi-resistance to at least two acaricide classes (range: 22.2–80.0%). Furthermore, resistance ratios (RR) showed high spatial variation (intercontinental, as well as regional) but low regional spatial autocorrelation. Previous and current acaricide use correlated with current RR, and several combinations of acaricide RR were positively correlated. Moreover, fipronil resistance tended to be higher in farms with more intense acaricide use. The kdr-mutations provided the ticks a fitness advantage under the selection pressure of synthetic pyrethroids based on population (kdr-allele frequency) and individual level data (genotypes). The data show the threat of acaricide (multi-)resistance is high in Brazil and South Africa, but acaricide specific levels need to be assessed locally. For this purpose, gathering complementary molecular information on mutations that underlie resistance can reduce costs and expedite necessary actions. In an era of human-caused habitat alterations, implementing molecular data-driven programs becomes essential in overcoming tick-induced socio-economic losses.The Bill & Melinda Gates Foundation (BMGF).https://www.elsevier.com/locate/ijpddrhj2024Veterinary Tropical DiseasesSDG-03:Good heatlh and well-bein

Carnivore population dynamics on two reserves, comparable or not?

Small carnivore species might provide the disease link in disease transmission between domestic dogs and apex predators. The objective of this study was to determine the presence of carnivores and prey species on two wildlife reserves in Mpumalanga Province. Carnivore presence was determined on two reserves managed by Mpumalanga Tourist and Parks Agency(MTPA). Manyeleti is contiguous with Kruger National Park (KNP), 23 000 hectares in area, and has villages on one side. Andover is not adjacent to KNP, 7 000 hectares in area, and has villages on three sides of the reserve. The presence of carnivores and determination of inter-species interactions were measured during a two-year period using randomly placed clusters of camera traps. These camera traps were placed at each selected location for a period of 4 to 6 weeks before being moved. Permanent camera traps were also placed on the interface between reserves and villages. Data were entered into Microsoft Excel and mapped using ArcGIS 10.4.1. Ordinary Kriging and inverse distance weighting interpolation were used to determine the spatial distributions of observed wildlife. The Mackenzie model was used to determine the daily detection probability of each species. The most abundant species present in Manyeleti were hyena (Crocuta crocuta) and Lion (Panthera leo). In Andover, the only apex predator present was leopard (Panthera pardus), while serval (Leptailurus serval), caracal (Felis caracal), and mongoose (Mungos mungo) were also present. Some locations were shared among carnivore species, while other areas had no carnivore species detected at all. Areas with prey species, water and access routes to water had the highest probability of carnivore detection.Poster presented at the University of Pretoria, Faculty of Veterinary Science Faculty Day, September 07, 2017, Pretoria, South Africa.Includes bibliographical referencesab201