Veterinary public health aspects related with food-producing wildlife species in the domestic animal, human and environment interface

Magwedere, Kudakwashe (2013-03)

Thesis (PhD)--Stellenbosch University, 2013.

Thesis

ENGLISH ABSTRACT: The wildlife industry in Namibia continues to grow as the production and consumption of game meat increases. However, the health risks posed by the trade in wildlife and related by-products to livestock and humans have not been fully assessed. The main objective of this study was to investigate the potential health risks related to the increased consumption of game meat and relevant by-products by assessing the quality of game meat, as well as determine the role of game meat species in the transmission of zoonoses. The microbiological quality and safety of export game meat was assessed. No differences in the aerobic plate count (APC) were observed between the years (2009 and 2010), but the mean Enterobacteriaceae count was 1.33±0.69log10 cfu/cm2 compared to 2.93±1.50log10 cfu/cm2 between the years. Insignificant heterotrophic plate count (HPC) levels were detected in 9/23 field water samples, while faecal bacteria (coliforms, Clostridium perfringens and enterococci) were not isolated in all samples. Seven serogroups, with the exception of O26, were detected in exotic species. A white tailed deer sample had a serotype belonging to O45 which confirmed positive for stx1 gene. In springbok, 5/15 pools of faecal samples tested positive for the intimin gene. No Salmonella spp were isolated, and all E. coli isolates from the meat samples were negative for STEC virulence genes (i.e. stx1, stx2, eae and hlyA). A linear regression analysis was conducted on selected variables to identify the main predictors and their interactions affecting pH of meat 4 hours post-slaughter. In an increasing order of magnitude during winter time, the pH reached at 16-36hr post slaughter in springbok heart, liver, spleen, kidney and lungs was significantly higher than pH 6.0, while no significant differences were observed from the regulatory reference (pH 6.0) in the heart. There was a positive association between the pH of game meat 4hr post-slaughter, and liver congestion. The pH of game meat 4hr post slaughter, increased by 0.11 units per mL increase in liver congestion, and decreased by 0.04 units per minute increase in the shooting to bleeding interval, irrespective of the species. Worm eggs of strongylids, Strongyloides papillosus, Toxocara spp, Trichuris spp and coccidia were found in variable numbers in both springbok and gemsbok faeces, indicating a potential risk of transmission to other species in the ecosystem. On examination of carcasses, a novel parasite, Skjabinodera kuelzii, was identified and noted to be associated with inguinal fascia and renal fat, but the public health significance remains unclear. Nevertheless, S. kuelzii should be considered as of potential significance during routine game meat inspection. A total of 12 310 springbok were harvested from 26 commercial farms over a period of two years. Tissue samples (i.e. 60 livers, 41 kidneys and 52 hindquarter muscles) were collected from randomly selected healthy animals. The mean values (i.e. above the detection limit) of cadmium (Cd) and lead (Pb) were 0.10±0.05mg/kg and 1.04±0.21mg/kg in the liver, respectively; and 0.33±0.22mg/kg and 0.905±0.51mg/kg in the kidney of springbok, respectively. The levels of cadmium and lead in the hindquarter muscles were below the detection limit. Serum samples (n=1692) collected from sheep, goats and cattle from four presumably at-risk farms, and 900 springbok (Antidorcas marsupialis) serum samples collected from 29 mixed farming units, were screened for Brucella antibodies by using the Rose-Bengal test (RBT). Positive cases were confirmed by complement fixation test (CFT). To assess the prevalence of human brucellosis, 137 abattoir employees were tested for Brucella antibodies using the standard tube agglutination test (STAT), and the enzyme linked immunosorbent assay (ELISA). Cattle and sheep from all four farms were negative by RBT and CFT, but two of the four farms carried 26/42 and 12/285 seropositive goats, respectively. Post mortem examination of seropositive goats revealed no gross pathological lesions. Culture for brucellae from organs of seropositive animals was negative. None of the wildlife sera tested positive by either RBT or CFT. Occurrence of confirmed brucellosis in humans was linked to the consumption of unpasteurized goat milk, home-made goat cheese and coffee with raw milk and prior contact with goats. All abattoir employees (n=137) tested negative by STAT, but 3 were positive by ELISA. The three abattoir workers were clinically normal, and lacked historical connections with clinical cases. This study illustrates the importance of microbiological, parasitic and residue monitoring as critical components of a hazard analysis and critical control point based system for game meat. The study also provides the basis for increased integrated health research, surveillance and meat safety risk analysis.

AFRIKAANSE OPSOMMING: Die Namibiese wildbedryf raak toenemend groter soos die produksie en verbruik van wildsvleis toeneem. Die verwante gesondheidsrisiko’s wat die gebruik van wildsvleis en verwante produkte vir mens en dier inhou, is nog nie volledig geassesseer nie. Die doelwit van die studie was om ondersoek in te stel na die potensiële gesondheidsrisiko's wat wildsvleis en verwante neweprodukte vir mens en dier inhou deur middel van die assessering van vleisgehalte en die bepaling van die rol van die wildsvleis spesies in die oordrag van soönoses. Die mikrobiologiese gehalte en veiligheid van uitvoer wildsvleis was geassesseer. Geen verskille in die aerobiese plaat telling (APC) vir monsters versamel tydens 2009 en 2010 is aangeteken nie. Die gemiddelde Enterobacteriaceae telling was 1.33± 0.69log10 cfu/cm2 in vergelyking met 2.93±1.50log10 cfu/cm2 tussen die jare. Onbeduidende heterotrofe plaattelling (HPC) vlakke is waargeneem in 9/23 water monsters, terwyl fekale bakterieë (d.i. kolivorme, Clostridium perfringens en enterokokke) nie in enige van die monsters geïsoleerd is nie. Sewe serogroepe, met die uitsondering van O26, is aangeteken vir die eksotiese spesies. Monsters verky van ʼn white tailed deer is as positief vir 'n serotipe van O45 getoets, en die teenwoordigheid van die stx1 geen is bevestig. In springbok het 5/15 poele van fekale monsters positief getoets vir die intimien geen. Geen Salmonella spp is geïsoleer nie en alle E. coli geïsoleer in die vleismonsters was negatief vir die Stec virulensie geen (d.i. stx1, stx2, EAE en hlyA). ʼn Liniêre regressie-analise is op geselekteerde veranderlikes wat as die belangrikste indikators kan dien, en enige moontlike interaksie wat die pH van wildsvleis 4 uur na-slag kan beïnvloed, uitgevoer. In 'n toenemende orde van grootte gedurende die winter tyd, die pH teen 16-36hr na slagting in springbok hart, lewer, milt, niere en longe was aansienlik hoër as die pH 6.0, terwyl geen beduidende verskille waargeneem is wanneer dit met die regulasie verwysingswaarde van die hart (pH 6.0) vergelyk is nie. Daar was 'n positiewe assosiasie tussen die pH van wildsvleis 4 uur na-slag en mate van aansameling in die lewer. Die pH van wildsvleis 4 uur na-slag, het toegeneem met 0.11 eenhede per mL toename in lewer aansameling en afgeneem met 0.04 eenhede per minuut toename in die skiet tot uitbloei interval, ongeag die spesie. Wurmeiers van rondewurms, Strongyloides papillosus, Toxocara spp, Trichuris spp en koksidia het in verskillende ladings in die mis van beide springbok en gemsbok ontlasting, voorgekom. Dit dui op 'n potensiële risiko van oordrag na ander spesies in die ekosisteem. Die voorkoms van ʼn nuwe parasiet, Skjabinodera kuelzii, in wildskarkasse is aangeteken en was geassosieer met inguinale fascia en renale vet, maar die openbare gesondheidsrisiko bly onduidelik. Daar word aanbeveel dat dié parasiet as ʼn potensiële risiko faktor tydens roetine vleisinspeksies beskou moet word. ʼn Totaal van 12 310 springbokke is oor 'n tydperk van twee jaar van 26 kommersiële plase geoes. Weefselmonsters (d.i. 60 lewers, 41 niere en 52 agterkwart spiere) is ewekansig versamel van gesonde diere. Die gemiddelde waardes (d.i. hoër as die opsporingslimiet) van kadmium (Cd) en lood (Pb) was 0.10 ± 0.05mg/kg en 1.04 ± 0.21mg/kg in die lewer onderskeidelik en 0.33 ± 0.22mg/kg en 0.905 ± 0.51mg/kg in die niere van springbok, onderskeidelik. Die vlakke van kadmium en lood in die agterkwart spiere was laer as die opsporingslimiet. Serum monsters (n=1692) is van skape, bokke en beeste van vier vermoedelik hoë risiko plase en springbok (Antidorcas marsupialis, n=900) van 29 gemengde boerdery sisteme versamel en getoets vir die teenwoordigheid van Brucella teenliggaampies deur middel van die Rose-Bengal-toets (RBT). Positiewe gevalle is bevestig deur die komplement binding toets (CFT). Die voorkoms van menslike brusellose is bepaal deur 137 abattoir werknemers te toets vir Brucella teenliggaampies deur gebruik te maak van die standaard buis agglutinasie toets (STAT) en die ensiembinding immunosorberende toets (ELISA). Beeste en skape van die vier hoë risiko plase het negatief getoets met die RBT en CFT metodes, maar bokke van twee van die vier plase het seropositief getoets (26/42 en 12/285 onderskeidelik). Nadoodse ondersoek van seropositief bokke het geen patologiese letsels aangedui nie. Die kultuur van orgaanmonsters van seropositief diere vir Brucellae was negatief. Die monsters versamel van wild het negatief getoets deur middel van die RBT en CFT toets metodes. Die voorkoms van brusellose in mense in die studie was geassosieer met die gebruik van ongepasteuriseerde melk, tuisgemaakte bokmelkkaas en koffie met ongepasteuriseerde melk, asook direkte kontak met bokke. Alle abattoir werknemers (n=137) het negatief getoets met die STAT metode, maar drie werknemers het positief getoets met die ELISA metode. Die drie abattoir werkers was klinies normaal en het nie vorige kontak met bevestigde kliniese gevalle gehad nie. Hierdie studie bevestig die belang van mikrobiologiese, parasitiese en residu monitering as kritieke komponente van 'n gevaar-analise en kritiese kontrolepunt gebaseerde stelsel vir die produksie en verbruik van wildsvleis. Die studie verskaf ʼn basis vir toekomstige navorsing gefokus op ʼn geïntegreerde benadering van mens- en diergesondheid, monitering en vleis veiligheid risiko-analises.

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