ABSTRACT
Tolerance to African animal trypanosomosis (AAT) among several animal species involves a
wide milieu of factors which modulate the animal’s response to the disease and is considered a
breed attribute. To investigate the effect of breed on tolerance/resilience to trypanosome
infection on pubertal boars, nine (9) Nigerian Native and nine (9) Large-White x Landrace
crossbreed 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 and
spermatogenic output including cell ratios and daily sperm production were studied over two
study periods- 63 days post infection (63d p.i.) and 98 days post infection (98d p.i.). Results
obtained indicated that infected boars of both breeds were clearly parasitaemic in the first study
period, with a significant (P<0.05) reduction observed in the native boars by 98d p.i. The general
trend 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. This
was not the case with the exotic Large-White x Landrace boars and suggested that the native
boars possessed a superior ability to mitigate the more severe effects of the pathology and a
tendency to return to normal. With respect to the clinical features investigated, the Nigerian
Native boars presented significantly (P<0.05) higher values with respect to parasitaemia log
values, rectal temperatures, as well as packed cell volume. Histopathological findings revealed
that lesions, including tubular distortion, denudation of basement membrane, seminiferous
epithelial damage led to the distortion of the architecture of the seminiferous epithelium as well
as 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 was
influenced by breed attributes. Biometrical and linear body measurements were affected
significantly (P<0.05) less in the native boars than in the exotic boars. Weight loss was
minimized among the native boars with a tendency to significantly (P<0.05) increase growth rate
as during the second study period, whereas this trend was not clearly observed among the exotic
boars. The effect of the infection on clinical and histopathological features, as well as growth
responses and especially in relation to the testes’ capacity for spermatogenesis was studied. We
observed significant (P<0.05) reductions in testes weight, somatic and germ cell populations and
also significant (P<0.05) reductions in the overall kinetics of spermatogenesis and daily sperm
production. The mechanisms of action implicated in breed responses to the pathology appeared
to relate to phenotypic characteristics as well as innate mechanisms which are known to
modulate the pathogenesis of trypanosomosis. Equally the lowered parasitaemia observed among
the native boars suggested that toxicological effects of trypanosomes on this breed of boars were
limited. It was concluded that the Nigerian Native boars possessed an attribute that could reverse
the 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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