EXPERIMENTAL TOXOPLASMOSIS IN BROILER CHICKS

To evaluate chicken toxoplasmosis both as an economic and a public hea lth subject, 84 broiler chicks of a commercial strain, 30 days old, we re distributed into seven groups of 12 birds (three replications of fo ur chicks) experimentally infected with three developing T. gondii sta ges of the P strain as follows: tachyzoites. intravenous (two groups: 5.0 x 10(5) and 5.0 x 10(6)), cysts, per os (two groups: 1.0 x 10(2) a nd 1.0 x 10(3)) and oocysts, per os (three groups: 5.0 x 10(2), 5.0 x 10(3) and 5.0 x 10(4)). Twelve chicks received only a placebo (control group). During the next 30 days the following parameters were estimat ed: productivity (weight gain and feed conversion), clinical signs, in cluding rectal temperature and parasitemia (bioassay). No clinical sig ns suggesting toxoplasmosis were seen and no statistical differences o n productivity standards were found in comparison between inoculated a nd control chicks. However, fowls inoculated with tachyzoites and oocy sts occasionally showed hyperthermia. Some haematological changes were detected in fowls inoculated with T. gondii. Anatomo-histopathologica l changes were not observed. From 14 parasitemias detected, 35.7% appe ared on the 5th day after inoculation and 57.1% of them resulted from oocysts inoculation. After 30-35 days all birds were slaughtered: frag ments from 12 organs or tissues from each of them were subjected to ar tificial peptic digestion and after that injected into T. gondii antib ody-free mice (IIFR). T. gondii was detected in brain (12), pancreas ( five), spleen (five), retina (five), kidney (two), heart (four), prove ntriculus (three), liver (two), intestine (two), lung (one), and skele tal muscle (one). Similar to observations with parasitemia, from 42 T. gondii isolations, 59.5% came from chicks which had received oocysts. It can thus be inferred that the developing form, expelled by cats, i s the most important for T. gondii chicken infection and that brain is the most infected organ in birds. Attention must be paid to the poten tial importance of chicken meat in public health, since T. gondii was isolated from skeletal and heart muscles. (C) 1997 Elsevier Science B. V.