Epizootiology, pathogenesis and immunoprophylactic trends to control tropical bubaline fasciolosis: an overview.

On the Indian sub-continent, nearly 5,000 years ago, the domestication of the riverine buffalo-the incredible Asian dairy animal was initiated. It plays a versatile role in socio-economic upliftment of its owners from the rural agricultural communities in Asian, African, South American and a few European countries. Comparatively, buffaloes are lesser evolved and susceptible to infectious diseases than cattle. However, poor body thermoregulation and wallowing nature predisposed them to snail borne infections, especially tropical fasciolosis-an incessant major constraint on buffalo production and improvement programmes. This review article is an insight into the global prevalence, varied epizootiological factors, offers possible explanation to pathophysiological clinical signs, deleterious effects of the tropical liver fluke, involving hepato-biliary system, haemopoitic system, endocrine glands and their secretions, oxidative stress, altered metabolism and significant fall in food conversion efficiency with unaffected digestibility of nutrients. Besides, the authors have briefly discussed and reviewed the developments and significance of successful immunodiagnostic approaches for detecting and forecasting the disease during early pre-patency and feasibility of developing a cost effective immunoprotection strategies against tropical fasciolosis.

Serum enzyme and hematological profile of Fasciola gigantica immunized and experimentally infected riverine buffaloes.

Sixteen male, yearling Murrah buffaloes were randomly assigned to four groups of four buffaloes each. Each animal in Gr-I and II were immunized, respectively, with 4.8 mg of excretory secretory antigen and 1,300 microg Infection Specific Antigen, in three divided doses. Subsequently, each animal in Gr-I, II, and III was per os infected with 800 viable Fasciola gigantica metacercariae (bubaline origin) on week-6 after the start of the experiment, while animals in Gr-IV served as healthy controls. The aspartate aminotransferase (AST) and alanine aminotransferase (ALT) concentrations progressively increased during the prepatency and respectively attained the highest levels during week-6 and 8 post-infection (PI). The alkaline phosphatase (AP) exhibited elevated trends from eighth week PI onward and continued to be higher until the end (p < 0.05-0.01). With the cessation of traumatic activities of the diastomes, the AST and ALT levels declined yet were throughout significantly higher than the healthy controls (p < 0.05-0.01). In the immunized animals (Gr-I and II), the fluctuation patterns were similar but the values were significantly lower than the non-immunized (Gr-III) animals (p < 0.05-0.01). The elevated levels of the enzymes had positive correlation with depressed erythrocytic indices, leucocytosis, eosinophilia, necropsy worm recovery, and hepatic lesion score in the respective groups. The increased concentrations of the enzymes revealed two clearly demarcated stages: (a) remarkably elevated AST (40.8%) and ALT (140.0%) levels during the prepatency, signifying traumatic lesions inflicted by the F. gigantica adolescercariae and (b) the significant increase in AP (107.9%), suggestive of bile duct hyperplasia, cholangitis, periportal fibrosis, and biliary obstruction etc. from sixth week PI onward. None of healthy controls developed clinical signs and had normal hematological and serum enzyme profiles. Diagnostic significance of these marker enzymes in the disease forecasting and in time application of control strategies to combat tropical fasciolosis in buffaloes in the endemic areas has been discussed.

Tropical liver fluke-induced stress in experimentally infected and immunised buffaloes.

Disease-related stress associated with Fasciola gigantica infection was investigated in 16 male, yearling Murrah buffaloes. The animals were randomly assigned to one of four groups. Animals in groups 1 and 2 were vaccinated subcutaneously with 4.8 mg of excretory-secretory antigen (group 1) or 1300 µg infection-specific antigen (group 2), in three doses. Subsequently, all the animals in groups 1, 2 and 3 were infected orally with 800 viable F gigantica metacercariae (bubaline origin) on week 6 of the experiment. The animals in group 4 served as healthy controls. The clinical progress of the disease with respect to the adrenocortical response to infection was assessed periodically. The infected animals in group 3 developed characteristic signs of the disease and had the highest in situ fluke population (mean [se] 331.8 [19.5] ). One of the four animals in group 3 died on day 110 postinfection (PI). Animals that had been immunised before infection (groups 1 and 2) acquired adequate levels of immunity, were comparatively healthier and had significantly lower (P<0.05) fluke populations (mean [se] 194.3 [11.8] in group 1 and 164.5 [9.2] in group 2). Throughout the course of the disease, the group 3 animals had significantly higher cortisol levels than those in groups 1 and 2 (P<0.01) from week 4 PI onward. Although animals in the immunised groups (groups 1 and 2) had increased hormone levels, they were not significantly different from those in the control animals in group 4. Cortisol levels were higher during the early prepatency phase (weeks 1 to 6 PI) than during the late prepatency and/or patency phases of the disease. Cortisol levels in the healthy control animals in group 4 remained within the normal range.