Toxoplasma gondii and Chlamydophila abortus in caprine abortions in Tobago: a sero-epidemiological study

A sero-epidemiological study was conducted on a goat farm that experienced an abortion epidemic in the 2005 breeding season in Tobago. Serum samples of goats (aborting and non-aborting) and cats were collected, in addition to the use of stored sera from the farm sampled in 2003 and 2004. Farm records on the reproductive and mortality rates for year 2003, 2004 and 2005 were also reviewed. The sera were screened for Toxoplasma gondii antibodies using the latex agglutination test (LAT), Chlamydophila abortus with an enzyme-linked immunosorbent assay (ELISA) and Brucella abortus using the buffered plate agglutination test (BPAT). Farm records revealed that for the period 2003-2005, the average kid per doe rate decreased from 2.1 to 1.5, the mortality rate increased from 6.3% in 2002 to 19.4% in 2004 and the fertility rate decreased from 98-99% (2002-2004) to 89% (2005). There was a dramatic increase in the abortion rate from <1% (2002, 2003 and 2004) to 29.2% (2005). Of a total of 161 sera tested comprising 12 from 2003, 89 from 2004 and 70 from 2005, 0 (0.0%), 21 (23.6%) and 45 (64.3%) were positive for T. gondii agglutinins (i.e. titres > or =1 : 64) and the differences were statistically significant (P < 0.05; chi(2)). Of all serum samples tested, only 1 (1.1%) of 89 from 2004 was positive for C. abortus while all the sera tested were negative for B. abortus. Amongst the 24 does which aborted in 2005 and were available for testing in mid-2005, 15 (62.5%) had reciprocal titres of > or =1 : 2048, three (12.5%) each had titres of 1 : 1024, 1 : 256 and < or =1 : 16 i.e. negative. The seroprevalence and titres of does that aborted, 20 (87.0%) of 23, all with titres > or =1 : 256 suggesting current infection, were statistically significantly (P < 0.05; chi(2)) higher than was detected amongst does that delivered normal kids, 25 (53.25) of 47 with 22 (48.8%) having titres of > or =1 : 256. One (50.0%) of two cats caught and tested was seropositive with a reciprocal titre of 128. This is considered the first documentation of T. gondii agglutinins in caprine abortion as well the detection of C. abortus antibodies from livestock in Trinidad. It is concluded that of the three zoonotic abortifacient pathogens tested for, T. gondii appeared to have played some aetiological role in the abortion epidemic investigated.