Prevalence of Antibodies to Toxoplasma gondii and Neospora caninum in Pigs in Grenada , West Indies

The aim of the study was to estimate the prevalence of antibodies to Toxoplasma gondii (T. gondii) and Neospora caninum (N. caninum) in pigs in Grenada, West Indies. T. gondii is a serious zoonosis affecting the unborn fetus and immunocompromized individuals. N. caninum is a similar coccidian parasite, which is not zoonotic, but is the cause of abortion and neonatal mortality in livestock similar to T. gondii. An earlier study conducted in Grenada and using a modified agglutination test (MAT) revealed seropositivity to T. gondii in pigs. No information is available on N. caninum infection of pigs in the Caribbean islands including Grenada. Serum samples from 185 pigs in Grenada, West Indies were tested for antibodies to T. gondii and N. caninum using an indirect enzyme linked immunosorbent assay (ELISA). Antibodies to T. gondii were found in 24.3% of pigs (95% confidence interval (CI): 18.12% to 30.48%) as all the tested pigs were negative for antibodies to N. caninum. Although, seroprevalence for T. gondii was higher in females (25.75%) than in males (20.70%), this result was statistically insignificant (p = 0.57). The results were similar to a previous study in Grenada confirming the continuity of infection in pigs. Human Toxoplasmosis is transmitted mainly through ingestion of tissue cysts in contaminated raw or undercooked meat or sporulated oocysts in soil, water or vegetables. Education of farmers and the Grenadian community on epidemiology of these parasites is warranted to prevent infection in pigs and in humans. This is the first report on the seroprevalence of N. caninum in pigs in the Caribbean region.


Introduction
Toxoplasmosis is a parasitic disease caused by proptozoa Toxoplasma gondii.The parasite infects warm blooded animals including humans.Human infection is mostly through ingestion of tissue cysts in contaminated raw or undercooked meat or sporulated oocysts in soil and water [1].In addition to the zoonotic potential of T. gondii, it causes mortality in neonatal pigs and reproductive failure in adult pigs.To the author's knowledge, there is limited data on the prevalence of T. gondii in pigs in the Caribbean countries.The seroprevalence of T. gondii in pigs was first reported in Trinidad [2] indicating seroprevalence of 5.5%.Chikweto et al. [3] using a modified agglutination test (MAT) reported seroprevalence of 23.1% in pigs in Grenada.
Neosporosis is an infectious disease primarily of cattle and dogs, and it has been reported rarely in other species [4] [5].N. caninum is not considered to be zoonotic.However, Helmick et al. [6] in UK while working on the prevalence of Neosposis in aborted sheep and swine reported 0.45% seropositivity to N. caninumin aborted sheep and 9.3% in aborted pigs, by ELISA, but all samples were negative when tested by IFAT.Damriyasa et al. [7] using ELISA reported a seropositivity of 3.3% for N. caninum in sows in Hesse Germany.To the authors' knowledge, there is no data on seroprevalence of N. caninum in pigs in the Caribbean countries.
The objective of this study is to estimate the seroprevalence of T. gondii and N. caninum in pigs from Grenada, West Indies.

Ethical Approval
The research project was approved by Institutional Animal Care and Use Committee (IACUC) of St. George's University, Grenada.

Collection of Samples
Grenada is the southernmost island country of the Southeastern Caribbean Sea.Its size is 344 Km 2 and the island is divided in 6 parishes.Jugular vein blood was collected from 185 pigs and after centrifugation at 3000 g for 5 minutes serum was removed and stored at −20˚C until analysis.Blood was collected from 53 boars and 132 sows, ranging in age from 6 months to 2 years.

Methodology
A Commercial Toxoplasma gondii multispecies ELISA kit and Neospora caninum multispecies ELISA kit from Pourquier Laboratories (IDvet, France) for detection of anti T. gondii and N. caninum antibodies were used according to the manufacturer's instructions.
All serum samples were negative for antibodies against N. caninum.

Discussion
A worldwide distribution of T. gondii has been reported based mainly on serological surveys [1].Seroprevalence of 23% in market pigs and 43% in breeder pigs, in the USA were detected during a survey in 1983-84.After a decade there was a decline in antibodies in pigs tested from the same areas [8].Good husbandry practices were attributed to this decline in seroprevalence of T. gondii.Like other food animals, pigs also get infected with T. gondii oocysts from cats.Pigs can also be infected through ingestion of infected rats [6] [9] and through feeding on milk from infected goats [10] [11].
Our results showed 24.3% (95% confidence interval [CI]: 18.12% to 30.48%) seropositivity for T. gondii in pigs using an ELISA, This is similar to the first study conducted by Chikweto et al. [3] in Grenada, in which a seroprevalence of 23.1% was reported using a MAT.There is considerable variation in the Seroprevalence of T. gondii from different countries of the world.In Germany it was found to be 19% ( [7]; in the USA, from 5% to 70.83 [1]; in Romania, 0.4% to 0.5% [12]; in Poland, 10.5% [13]; in Italy, 16.3% to 19% [14]; in the Netherlands, 2.6% [15]; 0.0% in Malaysia ( [16] and in Serbia, 9.3% [17].These variations are attributed to the type of husbandry, outdoor and indoor farms, access of cats to the farm, age of pigs, and the type of tests used for seroprevalence studies [1] [6]. Sera tested in the present study showed higher prevalence of antibodies to T. gondii in females compared to males, but this was statistically insignificant (p = 0.57).Published reports on association of gender and seroprevalence of T. gondii in pigs are scanty.Lonela et al. [9] reported a high seroprevalence of T. gondii in sows (80%) compared to boars (20%).Sergio et al. [18] in Brazil reported no association between gender and seroprevalence of T. gondii in pigs.
Canids are the final host of N. caninum.Livestock and wild animals get infected by consuming oocysts from infected canids.N. caninum is not zoonotic.Neosporosis is primarily a disease of cattle in which it is a major cause of abortion and reproductive disorders.Neosporosis in sheep and goats is asymptomatic.There have been reports on role of Neosporosis in abortion and neonatal mortality in adult sheep.However, the seroprevalence of N. caninum in sheep and goats varies from 0.6% to as high as 30.8% in various countries of the world [5].
There is paucity of published reports on Neosporosis in pigs.The few available reports indicate a very low seroprevalence of N. caninum in the swine population.Damariyasa et al. [7] reported a seropositivity of 3.3% pigs in Germany.Helmick et al. [6] reported seropositivity of 8.8% in pigs in the UK, but failed to confirm the seropositivity in that pig population by indirect fluorescent antibody test (IFAT) and an inhibition ELISA.A survey conducted in Brazil revealed a seroprevalence of 3.1% [18].To the authors' knowledge, there is no report on seroprevalence of N. caninum in pigs in Caribbean countries.This is the first report on the seroprevalence N. caninum in Grenada and the Caribbean region.

Conclusion
Pork is popular meat in Grenada and preferred when cooked through barbeque.The chances of survival of T. gondii oocysts in barbeque cooked meat are increased.Infected animals could thus transmit the disease to humans.

Recommendation
Pigs in Grenada are moderately exposed to T. gondii.Measures taken to prevent toxoplasmosis in humans should include education of pig farmers and the community at large.Pig farmers need to realize the role of cats and rodents in transmission of infection to pigs.Cats and rodent in free farms with good sanitary practices will aid in the prevention of toxoplasmosis in pigs and humans.Grenadians must be educated about the importance of complete cooking of pork before consumption.

Table 1 .
Seroprevalence of T. gondii in pigs in Grenada, West Indies.