Thesis Abstract

Thesis Overview

Tolerance to African animal trypanosomosis (AAT) among several animal species involves awide milieu of factors which modulate the animal’s response to the disease and is considered abreed attribute. To investigate the effect of breed on tolerance/resilience to trypanosomeinfection on pubertal boars, nine (9) Nigerian Native and nine (9) Large-White x Landracecrossbreed boars were experimentally inoculated with laboratory samples of Trypanosoma

brucei brucei.

Their comparative responses with regard to clinical symptoms, growth parameters,histopathological and histometrical features of the testis, Sertoli and germ cell numbers andspermatogenic output including cell ratios and daily sperm production were studied over twostudy periods- 63 days post infection (63d p.i.) and 98 days post infection (98d p.i.). Resultsobtained indicated that infected boars of both breeds were clearly parasitaemic in the first studyperiod, with a significant (P<0.05) reduction observed in the native boars by 98d p.i. The generaltrend in the results obtained showed significant (P<0.05) differences in the various parameters,with the Nigerian Native boars exhibiting strong marginal gains by the second study period. Thiswas not the case with the exotic Large-White x Landrace boars and suggested that the nativeboars possessed a superior ability to mitigate the more severe effects of the pathology and atendency to return to normal. With respect to the clinical features investigated, the NigerianNative boars presented significantly (P<0.05) higher values with respect to parasitaemia logvalues, rectal temperatures, as well as packed cell volume. Histopathological findings revealedthat lesions, including tubular distortion, denudation of basement membrane, seminiferousepithelial damage led to the distortion of the architecture of the seminiferous epithelium as wellas degradation of the inter-tubular compartment and values were significantly (P<0.05) lower

among the native boars.

The parameters on growth showed the nutrient-parasite interaction wasinfluenced by breed attributes. Biometrical and linear body measurements were affectedsignificantly (P<0.05) less in the native boars than in the exotic boars. Weight loss wasminimized among the native boars with a tendency to significantly (P<0.05) increase growth rateas during the second study period, whereas this trend was not clearly observed among the exoticboars. The effect of the infection on clinical and histopathological features, as well as growthresponses and especially in relation to the testes’ capacity for spermatogenesis was studied. Weobserved significant (P<0.05) reductions in testes weight, somatic and germ cell populations andalso significant (P<0.05) reductions in the overall kinetics of spermatogenesis and daily spermproduction. The mechanisms of action implicated in breed responses to the pathology appearedto relate to phenotypic characteristics as well as innate mechanisms which are known tomodulate the pathogenesis of trypanosomosis. Equally the lowered parasitaemia observed amongthe native boars suggested that toxicological effects of trypanosomes on this breed of boars werelimited. It was concluded that the Nigerian Native boars possessed an attribute that could reversethe adverse patho-physiological effects of T. b. brucei infection and were therefore more resilient

to T. b. brucei infection than the exotic Large-White x Landrace boars.

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ABSTRACTTolerance to African animal trypanosomosis (AAT) among several animal species involves awide milieu of factors which modulate the animal’s response to the disease and is considered abreed attribute. To investigate the effect of breed on tolerance/resilience to trypanosomeinfection on pubertal boars, nine (9) Nigerian Native and nine (9) Large-White x Landracecrossbreed boars were experimentally inoculated with laboratory samples of Trypanosoma

brucei brucei.

Their comparative responses with regard to clinical symptoms, growth parameters,histopathological and histometrical features of the testis, Sertoli and germ cell numbers andspermatogenic output including cell ratios and daily sperm production were studied over twostudy periods- 63 days post infection (63d p.i.) and 98 days post infection (98d p.i.). Resultsobtained indicated that infected boars of both breeds were clearly parasitaemic in the first studyperiod, with a significant (P<0.05) reduction observed in the native boars by 98d p.i. The generaltrend in the results obtained showed significant (P<0.05) differences in the various parameters,with the Nigerian Native boars exhibiting strong marginal gains by the second study period. Thiswas not the case with the exotic Large-White x Landrace boars and suggested that the nativeboars possessed a superior ability to mitigate the more severe effects of the pathology and atendency to return to normal. With respect to the clinical features investigated, the NigerianNative boars presented significantly (P<0.05) higher values with respect to parasitaemia logvalues, rectal temperatures, as well as packed cell volume. Histopathological findings revealedthat lesions, including tubular distortion, denudation of basement membrane, seminiferousepithelial damage led to the distortion of the architecture of the seminiferous epithelium as wellas degradation of the inter-tubular compartment and values were significantly (P<0.05) lower

among the native boars.

The parameters on growth showed the nutrient-parasite interaction wasinfluenced by breed attributes. Biometrical and linear body measurements were affectedsignificantly (P<0.05) less in the native boars than in the exotic boars. Weight loss wasminimized among the native boars with a tendency to significantly (P<0.05) increase growth rateas during the second study period, whereas this trend was not clearly observed among the exoticboars. The effect of the infection on clinical and histopathological features, as well as growthresponses and especially in relation to the testes’ capacity for spermatogenesis was studied. Weobserved significant (P<0.05) reductions in testes weight, somatic and germ cell populations andalso significant (P<0.05) reductions in the overall kinetics of spermatogenesis and daily spermproduction. The mechanisms of action implicated in breed responses to the pathology appearedto relate to phenotypic characteristics as well as innate mechanisms which are known tomodulate the pathogenesis of trypanosomosis. Equally the lowered parasitaemia observed amongthe native boars suggested that toxicological effects of trypanosomes on this breed of boars werelimited. It was concluded that the Nigerian Native boars possessed an attribute that could reversethe adverse patho-physiological effects of T. b. brucei infection and were therefore more resilient

to T. b. brucei infection than the exotic Large-White x Landrace boars.