TOXOPLASMOSIS IN POTHWAR REGION: A SERO-EPIDEMIOLOGICAL STUDY OF Toxoplasma gondii IN DIFFERENT ANIMALS WITH SPECIAL REFERENCE TO ITS ZOONOTIC POTENTIAL

Abstract

Toxoplasmosis is a cosmopolitan zoonotic infection caused by a coccidian protozoan Toxoplasma gondii which affects a wide range of hosts including humans, all other mammals and birds. The main route of transmission to herbivorous animals is through ingestion of sporulated oocysts. However the infection can also be transmitted to carnivorous or omnivorous hosts via consumption of tissue cysts present in meat. Wild and domestic cats are the principal reservoir where oocysts are produced during sexual phase of lifecycle. The infection is considered nonexistent or rare without cats. Livestock animals when infected during pregnancy are suffered from parasitemia which can infect placenta and fetus that ultimately results in fetal resorption, miscarriage, death or mummification. Apart from being hazardous to livestock animals the T. gondii infection is also important due to its zoonotic implications. Congenital abnormalities in humans such as microcephaly, hydrocephaly, chorioretinitis, convulsion, cerebral calcification, epilepsy, blindness, deafness and mental retardation may occur if the mother acquires infection during pregnancy. Apart from congenital anomalies, T. gondii also causes severe neuropathologic infections in immunocompromised hosts such as AIDS patients and the patients of cancer undergone chemotherapy. Current study was designed to workout the sero- epidemiology of Toxoplasma gondii in sheep, goats, cattle, buffaloes, cats, dogs and humans in northern parts of Pakistan because no such work previously exists in the country. For this purpose serum samples from 413 sheep, 419 goats, 400 cattle, 422 buffaloes, 408 dogs, 420 cats and 1659 humans were screened for presence or absence of Toxoplasma-specific IgG and IgM antibodies by using enzyme-linkedxxiii immunosorbent assay (ELISA). Additional data related to various possible risk factors in all the studied hosts was obtained on questionnaire by surveys and interviews. Multivariate logistic regression model was applied to associate the infection with possible risk factors. Overall prevalence of infection was 18.16 percent in sheep (75/413), 14.32 percent (60/419) in goats, 19.75 percent (79/400) in cattle, 15.17 percent (64/422) in buffaloes, 28.43 percent (116/408) in dogs, 26.43 percent (111/420) in cats and 20.37 (338/1659) in humans. Seroprevalence did not vary significantly in all hosts in four districts. A steady increase in seroprevalence was observed in all hosts with increasing age. Prevalence was high in female sheep, goats, cattle and buffaloes as compared to males. No difference of seroprevalence in different breeds of livestock was observed except Salt Range (P<0.05, OR=5.51) sheep which showed more than five fold high prevalence as compared to other breeds of sheep. Risk factors which were significantly associated with T. gondii infection in livestock animals were poor hygienic conditions (all livestock species), outdoor water sources (goats), presence of cats in vicinity (all livestock species), extensive management system (all livestock species), pregnancy (sheep and buffaloes) and large herd size (sheep and goats). In cats and dogs seroprevalence was also high in animals older than one year. Risk factors which significantly associated with T. gondii infection in pet animals were rural area (dogs) and excess to outside (cats and dogs). Seroprevalence also increased with age in humans and was also high in females. Risk factors which were significantly associated with seroprevalence were occupation, low level of education (P<0.05, OR=2.32), consumption of mutton, outdoor water sources (P<0.05, OR=1.97), high meat eating frequency (P<0.05, OR=2.73), preference forxxiv undercooked meat (P<0.05, OR=2.11), availability of cats in surroundings (P<0.05, OR=1.42), soil exposure (P<0.05, OR=1.82), pregnancies (P<0.05, OR=7.60) and abortions (P<0.05, OR=5.00). T. gondii infection was high in post rainy seasons with high temperature, abundant rainfall and high percentage of relative humidity. The results from present study show that T. gondii infection is widespread in all the possible hosts in Pakistan and have important application for livestock industry and public health.