Babesia kiwiensis, PEIRCE & JAKOB-HOFF & TWENTYMAN, 2003

PEIRCE, M. A., JAKOB-HOFF, R. M. & TWENTYMAN, C., 2003, New species of haematozoa from Apterygidae in New Zealand, Journal of Natural History 37 (15), pp. 1797-1804 : 1798-1800

Babesia kiwiensis sp. nov.

(figures 1–14)

Parasite. Babesia kiwiensis sp. nov. Type host. Apteryx australis mantelli Bartlett. Type locality. Purua, North Island, New Zealand. Vector. Probably Ixodes anatis Chilton. Hapantotypes. IRCAH : G463194 from Apteryx australis mantelli , coll. Twentyman, 21 February 2000, Auckland Zoo, New Zealand; IRCAH: G463195 from Apteryx australis mantelli , coll. Jakob-Hoff, 29 November 2000, Auckland

Zoo, New Zealand. Deposited in the International Reference Centre for Avian Haematozoa, Queensland Museum, Brisbane, Australia.

Parahapantotypes. IRCAH: G463196 from Apteryx australis mantelli , coll. Twentyman, 18 February 2000, Auckland Zoo , New Zealand ; IRCAH: G463197 - G463199 from Apteryx australis mantelli , coll. Jakob-Hoff, 29 November 2000, Auckland Zoo , New Zealand . Deposited in the International Reference Centre for Avian Haematozoa, Queensland Museum, Brisbane, Australia .

Distribution. Probably occurs throughout New Zealand with potential to infect all species of Apterygidae .

Description. The smallest parasites seen are ring forms comprising compact masses of chromatin with a small amount of pale central cytoplasm measuring 1.2 m m. These grow in size maintaining a generally round form (figure 1) in which the chromatin divides (figures 2, 7) giving rise to schizont precursors which have usually four distinct chromatin masses (figures 3, 8) and a pale cytoplasm. These round forms measure up to 2.76 m m (mean 2.16 m m) (N =30). Occasionally amoeboid tetrad forms (figures 4, 9) may occur. Schizonts produce three (figures 5, 11) or more usually four (figures 6, 10) pyriform merozoites in a cruciform configuration although the angle between adjacent pairs is not equal. Maximum diameter of cruciform schizonts is 3.36× 2.88 m m. The pyriform merozoites separate (figures 12–14) and each measures 1.35–1.95× 0.72–1.11 m m (mean 1.62× 0.90 m m) (N =20). The nucleus in merozoites is always proximal. Once separated from the schizont the merozoites gradually become round, invade new erythrocytes and the cycle is repeated as development progresses. Multiple invasion of erythrocytes has not been observed and there appears to be little or no displacement of the host cell nucleus.

Comments. The limited clinical observations on the small number of birds studied does not indicate that Babesia kiwiensis sp. nov. is pathogenic, although with concomitant infections with other disease agents it may contribute to chick morbidity. Studies are continuing to determine the life cycle of the parasite and to investigate the possibility that I. anatis is the vector. Heavy tick infestations with this species may be significant in chick morbidity due to blood loss anaemia and other clinical manifestations (see Jakob-Hoff et al., 2002).