Toxoplasmosis and neosporosis among beef cattle slaughtered for food in Western Thailand.

Beef is a main type of meat consumed by Thais. The prevalences of anti-Toxoplasma gondii and anti-Neospora caninum antibodies were investigated among beef cattle slaughtered for food in western Thailand. A total of 389 blood samples obtained from beef cattle from 24 herds were collected at 3 slaughterhouses in 3 western provinces of Thailand: Kanchanaburi, Ratchaburi and Nakhon Pathom. An indirect immunofluorescent antibody test (IFAT) was performed using cut-off values of 1:128 for T. gondii and 1:200 for N. caninum. The antibodies to T. gondii were found in 100 samples (25.7%) and antibodies to N. caninum were found in 23 samples (5.9%) a significant difference (p < 0.001) in prevalences, indicating the cattle tested had a greater exposure to T. gondii than N. caninum, and they should be regarded as a potential source of T. gondii infection to humans. The low prevalence of neosporosis in this study is still a risk for morbidity among cattle, including abortions. This is the first study in Thailand finding both T. gondii and N. caninum antibodies among beef cattle.

Transplacental transmission in cattle: is Toxoplasma gondii less potent than Neospora caninum?

We compared the transplacental-transmission ability of Toxoplasma gondii and Neospora caninum in cattle. One uninfected pregnant heifer served as control, while three were inoculated with N. caninum K9WA strain and four with T. gondii RH strain at their midgestational period. Both infected groups showed clinical signs and antibodies either to N. caninum or T. gondii, while the control animal was normal. Two (50%) Toxoplasma dams aborted on days 6 and 11 postinoculation. T. gondii tachyzoites were found in various organs of those dams that had abortions but not in their fetuses. Two Neospora dams did not abort but gave birth to subclinically infected calves. The remaining two Toxoplasma dams and one from Neospora group became recumbent. Those two dams and their fetuses showed disseminated Toxoplasma DNA, but no Neospora DNA was found. Our findings suggest that maternal toxoplasmosis could be a cause of abortion and congenital toxoplasmosis in cattle, especially when they are infected by virulent strains.

Sensitivity and specificity of polymerase chain reaction for the detection of Toxoplasma gondii DNA added to laboratory samples.

We studied the sensitivity and specificity of PCR to detect T. gondii DNA by aliquoting various concentration of tachyzoites into laboratory specimens from 60 positive and 10 negative buffy-coat samples. We were able to detect the specific gene from purified DNA samples containing as few as 0.25 parasites per 100,000 human leukocytes. These results had an impressive initial 100% specificity but later it decreased because of false-negative data.

PCR technique for detecting Toxoplasma gondii in animal amniotic fluid.

The goal of diagnosing congenital toxoplasmosis is early detection of maternofetal transmission, for early treatment to prevent unwanted sequelae. Polymerase chain reaction (PCR) is a method used recently for detecting toxoplasmosis during pregnancy. Amniotic fluid is a the clinical specimen used, since it provides a rapid, simple and safe method to obtain accurate results. The advantages of the PCR technique are high sensitivity, specificity and positive predictive value compared with other laboratory methods. To determine the sensitivity, specificity and lower detection limits in our laboratory, amplification of the B1 gene by nested PCR was performed on Toxoplasma gondii tachyzoites added to animal amniotic fluid samples. From 48 samples, our technique detected T. gondii in 30 out of 41 positive samples, and gave negative results for all the negative samples. The sensitivity for this nested PCR was 73%, the specificity was 100%, and the efficiency of the test was 77.1%. The nested PCR technique is recommended as a diagnostic method for detecting T. gondii in suspected congenital toxoplasmosis animals.