Immunoprophylaxis against common dog tick using gut antigen

Abstract

The occurrence of tick infestation in dogs in the Corporation of Thrissur, Kerala, India, was studied in 1200 dogs during a period of one year from July 2004 to June 2005. Four hard tick species viz Rhipicephalus sanguineus, R. haemaphysaloides, Haemaphysalis bispinosa, H. bispinosa var. intermedia were identified. Significant difference in species wise prevalence was found on 124 tick positive dogs. The most prevalent species of tick infesting dogs was found to be R. sanguineus (8.58 per cent) followed by H. bispinosa (1.33 per cent), R. haemaphysaloides (0.33 per cent) and H. bispinosa var. intermedia (0.08 per cent). Three species of ticks namely R. haemaphysaloides, H. bispinosa, and H. bispinosa var. intermedia have been recorded in dogs for the first time from Kerala. The influence of month, season, age, gender and breed on the prevalence rate were observed. Prevalence rates were calculated by month, season, age, gender and breed. No significant difference (P>0.05) of tick infestation during different months was observed due to temperature, relative humidity, and rainfall. No clear pattern of seasonality was observed for R. sanguineus, which was present throughout the year. The different variables considered in the present study such as age and gender were not significantly associated with the presence of tick infestation in dogs. There was a highly significant (P<0.01) association between breed and the intensity of infestation with maximum intensity of infestation in German shepherd dogs. Sites of attachment of ticks were ear, neck, interdigital space, dorsum of the body, eyelids, perianal region, withers, thorax and hind limbs. Highly significant variation (P<0.01) was observed between attachment sites with maximum on ear (84.68 per cent) followed by neck and interdigital space. Tick-bite naive guinea pigs inoculated with gut extracts and Freund’s adjuvant revealed induced immunity against R. sanguineus expressed by altered feeding and fertility parameters consisting of the prolonged engorgement period, reduced engorged female weight and feeding efficiency index, prolonged pre oviposition period, reduced oviposition period, egg mass weight, egg rate conversion efficiency and larval mass. Except the incubation period all the reproductive and feeding parameters differed significantly compared to the control. Inradermal test done on immunised guinea pigs to assess cell mediated immunity revealed both immediate and delayed hypersensitivity reaction. Humoral immune response assessed by agar gel immunodiffusion (AGID) and passive haemagglutination (PHA) revealed that the former was less sensitive compared to the latter. Passive haemagglutination test detected anti tick antibodies as early as 14th day post immunisation. Peak titre 1:128 reached on the 35th day post immunisation.