ISOSPORA-THIBETANA N. SP. (APICOMPLEXA, EIMERIIDAE), A PARASITE OF THE TIBETAN SISKIN (SERINUS-THIBETANUS EQUALS CARDUELIS-THIBETANUS) (PASSERIFORMES, FRINGILLIDAE)
S. Perrucci et al., ISOSPORA-THIBETANA N. SP. (APICOMPLEXA, EIMERIIDAE), A PARASITE OF THE TIBETAN SISKIN (SERINUS-THIBETANUS EQUALS CARDUELIS-THIBETANUS) (PASSERIFORMES, FRINGILLIDAE), The Journal of eukaryotic microbiology, 45(2), 1998, pp. 198-201
Tibetan siskins are birds native to the Himalayan region often importe
d into Italy for commercial purposes. Fecal examination of 45 imported
subjects with clinical signs of diarrhoea revealed the presence of a
large number of coccidian oocysts. After sporulation, accomplished by
mixing feces with 2.5 % (w/v) acqueous K2Cr2O7 at room temperature (22
degrees C +/- 1 degrees C), exogenous stages of an Isospora species w
ere revealed. The oocysts of this Isospora are spherical, have a bilay
ered colorless wall, and average 23.24 mu m x 23.05 mu m: oocyst resid
uum and micropyle an absent, while an oval polar granule is rarely pre
sent. The elliptical sporocysts average 18.44 mu m x 10.97 mu m and th
e Stieda body protrudes slightly from the end of the sporocyst. A sphe
rical sporocyst residuum is present though it sometimes consists of sc
attered granules. The spindle-shaped sporozoites average 11.53 mu m x
2.86 mu m, and have two refractile bodies. The taxonomic position of t
he tibetan siskin is controversial. Some authors include this species
in the genus Serinus, while others include it in the genus Carduelis.
The coccidian species isolated from these tibetan siskins was, for thi
s reason, compared with the Isospora species previously described both
in the genus Carduelis and in the genus Serinus. As a result of this
comparison a new species, Isospora thibetana, was named. In the intest
ine of dead subjects, oocysts were found only in the ileum where the m
ucosa was greatly thickened and presented a heavy leucocytic infiltrat
ion consisting mainly of lympho-monocytic cells. A similar infiltratio
n was observed in liver and lungs as well.