A Study on Toxoplasma gondii and Neospora caninum in Dairy Cows and Co-herded Camels, Sheep and Goats: Special Emphasis to Seroprevalence Risk factors and Serological Co-existence with Brucella abortus

Abstract

Toxoplasma gondii and Neospora caninum are closely related intracellular parasites which cause reproductive failure in man and animals worldwide. The aim of this study was to determine the sero-epidemiology of these parasites in dairy cows, and the co-herded camel, sheep and goats in the Sudan. Serological survey to detect antibodies against these parasites was carried out using different serological tests. The possible potential risk factors and the association between the seropositivity of these parasites and B. abortus infection were also analyzed using questionnaire and the available data of brucellosis from the concurrent research project. The present study is the first large scale report on serological evidence of both T. gondii and N. caninum infection associated with B. abortus infection in dairy farms from the Sudan as well as the risk factors associated with their seropositivity. The study revealed that, the overall seroprevalence of T. gondii infection at herd level of dairy animals in the State was 92.7%. The within herd seroprevalence was ranging from 8% up to 100% with mean of 51.3±24.3% in different herds of different dairy animals species in the State. The differences between the three districts, the seven localities and the four animal species were statistically highly significant (p<0.01). The overall sero-prevalence of T. gondii infection in dairy animals –at individual level- was 45.3%. Sheep scored the highest seroprevalence rate (75.0%) followed by goats (64.0%), camels (54.1%) and cattle (40.9%) with high statistically significant differences (p<0.01). The highest level of antibody titration (1:128) was reported in sheep and goats. The LAT and ELISA tests detected relatively similar proportion of Toxoplasma positive serum samples of dairy cows. The level of agreement between the two tests as well as the area under the ROC curve was found to be fair and associated with the level of antibody titration recorded by LAT. The univariate analysis included region, herd type, source of fodder, source of water, neosporosis, keeping cats, stray cats, keeping both dogs and cats and presence of both stray dogs and cats as risk factors associate with positive status of T. gondii infection. However, the multivariate analysis indicated region (Omdurman, p=0.000 and Bahri, p=0.044), Animal species (sheep, p=0.006) as the significant (p<0.05) risk factors of T. gondii seropositivity. The overall seroprevalence of N. caninum at herd and individual level of dairy animals in the present work was 32.2% (56/174) and 8.8% (80/906) respectively. The within herd seroprevalence was ranging from 7% up to 75% with mean of 27.2±15.4 in different herds of different dairy animals species. The highest percent inhibition (pi) recorded was 93% with mean of 38.7±12.3 and 39.3±13.9 at herd and individual level respectively. The highest prevalence rate, frequency distribution of the prevalence rate and the pi was reported in cattle at both herd and individual level followed by camel, goats and sheep respectively. Interestingly, camel was relatively similar to cattle in the occurrence of N. caninum infection in this study. There were no significant differences in the seroprevalence of N. caninum among the three districts, the seven localities and the four animal species (p>0.05). The univariate analysis included Production system, source of concentrate, keeping dogs, other diseases (Toxoplasmosis) as risk factors associated with cELISA positive status of N. caninum infection. The multivariate analysis indicated only production system (Intensive, p=0.019) and source of concentrate (Readymade, p=0.007) as the statistically significant (p<0.05) risk factors of being Neospora cELISA positive. Mix-infection was observed in 176 heads (19.7%) out of all 895 seropositive animals and in 149 (47.9%) out of the 311 B. abortus seropositive ones. Out of these 9 (6.04%) animals harbour the antibodies of the three abortifacient agents (T. gondii, N. caninum and B. abortus). Additionally 39 (48.8%) animals out of the 80 N. caninum seropositive animals have mix-infection with T. gondii. The univariate analysis showed no significant (p>0.05) association between B. abortus seropositivity and the two protozoal abortifacients. However, significant (p=0.041) association was observed between N. caninum seropositivity and T. gondii infection. Increasing odds ratios without significant (p>0.05) associations were observed in the multivariate analysis. Different reproductive problems (abortion and repeated abortion, repeat breeding, stillbirth and neonatal mortalities were reported during interview with the owners of the investigated dairy herds. Interestingly, 58% of the interviewed farmers send their dairy animals with reproduction problems to slaughter houses. With the exception of B. abortus the other causes of reproduction failure were neglected. Generally, this is the first comprehensive data explaining the association between N. caninum, T. gondii, their risk factors and B. abortus seropositivity in dairy animals from the Sudan. In addition, this study documents for the first time the existence of antibody against N. caninum in camels, sheep and goats in the Sudan. In conclusion, the results obtained in this study confirm the wide spread nature of T. gondii and N. caninum exposure together with B. abortus among dairy animals in the Sudan. This indicates the need for further work to identify appropriate bio-security measures to prevent transmission to human and industrial animals, thus reducing the economical consequences of these abortifacient agents in the country.