The zoonotic potential of Trichinella zimbabwensis as supported by the clinical symptoms observed in experimentally infected, non-human primates (Mukaratirwa et al., 2001) necessitates research aimed at elucidating the distribution and epidemiology of this parasite. No controlled studies have been conducted to determine the predilection muscles of Trichinella zimbabwensis larvae in Nile crocodiles (Crocodylus niloticus) or the influence of infection intensity on the distribution of the larvae in crocodiles. Neither has the influence of Trichinella zimbabwensis on biochemical parameters in crocodiles been assessed previously. To determine the distribution patterns of Trichinella zimbabwensis larvae and predilection muscles and to assess the influence on selected biochemical parameters, fifteen crocodiles were randomly divided into three cohorts of five animals each to represent high infection (642 larvae/kg of body weight), medium infection (414 larvae/kg of bodyweight) and low infection (134 larvae/kg of bodyweight) cohorts. In the high infection cohort, high percentages of larvae were observed in the tricep muscles (26%) and hind limb muscles (13%). In the medium infection cohort, high percentages of larvae were found in the tricep muscles (50%), sternomastoid (18%) and hind limb muscles (13%). For the low infection cohort, larvae were mainly found in the intercostal muscles (36%), longissimus complex (27%), forelimb muscles (20%), and hind limb muscles (10%). Predilection muscles in the high and medium infection cohorts were similar to those reported in naturally infected crocodiles despite changes in infection intensity. The high infection cohort had significantly higher numbers of larvae in the intercostal, longissimus complex, external tibial flexor, longissimus caudalis and caudal femoral muscles (P < 0.05) compared to the medium infection cohort. In comparison to the low infection cohort, the high infection cohort harboured significantly higher numbers of larvae in all muscles (P < 0.05) except for the tongue and pterygoid. The high infection cohort harboured significantly higher numbers of larvae (P < 0.05) in the sternomastoid, tricep, intercostal, longissimus complex, external tibial flexor, longissimus caudalis and caudal femoral muscles compared to naturally infected crocodiles. The importance of host characteristics in determining predilection and the importance of leg musculature as a predilection site for Trichinella spp. in sylvatic carnivores were both confirmed in this study. Deviations from normal parameters of blood glucose, alanine transaminase (ALT), aspartate transaminase (AST), creatine phosphokinase (CPK) and lactate dehydrogenase (LDH) compared to observations in uninfected reptiles were observed. Hypoglycaemia was not observed in the infected groups in this study. The humoral immune response to Trichinella zimbabwensis infection was evaluated in all three groups by way of indirect ELISA. Peak values of blood glucose, LDH and AST were observed on day 56, 49 and 42 p.i. in the high, medium and low infection cohorts respectively. CPK values peaked on day 35 p.i. in all three cohorts. Peak ALT values were reached on day 56 in the high infection cohort and on day 28 p.i. in both the medium and low infection cohorts. No correlations between the biochemical parameters and infection intensity were observed. Peak antibody titres were reached on day 49 p.i. in the medium infection cohort and on day 42 p.i. in both the high and low infection cohorts. Infection intensity could not be correlated with the magnitude of the humoral immune response or time to seroconversion. The effect of infection intensity on time to seroconversion, magnitude and persistence of the humoral immune response was assessed. No significant differences in the titre levels between the three groups were observed. Infection intensity could not be correlated with the magnitude of the humoral response or time to seroconversion. Results of this study were in agreement with results reported in mammals (wild boars and horses) infected with other Trichinella species and showed that antibody titres could not be detected indefinitely. / Thesis (M.Sc.)-University of KwaZulu-Natal, Westville, 2013.

The American kestrel (Falco sparverius) - Trichinella pseudospiralis host-parasite association was used as a model to study the effect of infection on (1) mate choice of female kestrels and (2) competitive abilities of male kestrels. In 34 choice tests, female selection of infected or uninfected males was random. Male competitive abilities was assessed by observing interactions between infected and uninfected individuals in a pen with a caged female and a single nest box. In 8 of 11 trials, uninfected males spent more time in the section closest to the female than their infected rivals, and performed more chases, attacks, and displacements than the latter. These results suggest that variation in male quality is determined in part by resistance to parasitism and can affect competition for nesting territories. Females may not have evolved mechanisms to detect parasitized males because these males are unlikely to outcompete uninfected males when territories are in limited supply.

This study investigated the predatory behaviour of kestrels on insect prey in a modified open-field arena, and assessed the effects of T. pseudospiralis infections on the sequence of predatory behaviours, hunting efficiency and choice of hunting method of the birds. Choice of hunting method in kestrels was related to their appraise energy expenditure and relative success. Hunting from a perch was more common, presumably less strenuous and more successful than hunting afoot. Hunting prey confined to the vertical walls of the arena was considered more strenuous and was less successful than hunting freely-roaming ground prey. Infection with T. pseudospiralis did not affect attack rate or hunting success but altered the manner in which prey were taken. Thus, the frequency of strikes performed in level flight declined, and birds tended to hunt more on foot. In flight, the frequency of wing beats and the horizontal distance travelled to regain the elevated perch increased. Concordance was found between intensity of infection and magnitude of change in body weight and flight activities. (Abstract shortened by UMI.)

Thesis (Ph.D. (Tropical Medicine))--Mahidol University, 2003.

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The host eosinophil response was compared in mice infected with either T. spiralis or T. pseudospiralis by determination of levels of splenic and intestinal phospholipase B, a marker enzyme for eosinophils. Primary infection of naive mice and challenge infection of homologously sensitized mice with T. pseudospiralis resulted in significantly lower tissue phospholipase B activities than infection with T. spiralis. Mice homologously challenged with T. pseudospiralis did exhibit an anamnestic eosinophil response compared to mice given a primary T. pseudospiralis infection. This anamnestic response, however, was significantly lower than the eosinophil response seen in sensitized mice given a homologous T. spiralis challenge. Mice sensitized to T. spiralis or T. pseudospiralis and heterologous challenge demonstrated an elevated eosinophil response compared to mice given a primary infection with either parasite. The heterologous challenge response, however, was not as intense as found for sensitized mice given a homologous challenge.

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