Aspectos morfológicos, biológicos e epizootiológicos de Parahaemoproteus nettionis (Johnston & Cleland,1909) (Haemosporidiidea: Haemoproteidae) em Cairina moschata L. no Brasil

Abstract

Infections of Parahaemoproteus nettionis (Johnston & Cleland, 1909), recorded on the basis of the presence of mature gametocytes, were encountered only in Cairina moschata of more than 40 days old. The occurrence of this parasite was recorded in the State of Rio de Janeiro, the State of São Paulo and in the Federal Territory of Roraima, with a calculated prevalence of 22,4% for all material examined. The highest indices of occurrence were observed in March and April, the period corresponding with the final phase of the population peak of blood-sucking insects in the enzootic areas. Biological tests under experimental conditions showed that Culex fatigans is not an efficient transmittor. Due to the poor survival of simulids and ceratopogonids in the laboratory and to the difficulty of proving the feeding of these dipterans on C. moschata, it was not possible to demonstrate the development of P. nettionis in these probable vectors. 77 In the erythrocytes of the host only sexual forms of the parasite were observed. Inoculations of blood, or of suspensions of macerated organs from birds known to be parasitised, were inadequated for the transmission of the parasite. The exflagellation of the microgametocytes of P. nettionis could be observed after two minutes and thirty seconds, with emissions of up to eight microgametes. It was noted that P. nettionis is hardly pathogenic for C. moschata, although the sexual forms encountered in the erythrocytes cause an increase in the size of the parasitised cell, frequently displacing their nuclei. Additionally, it was show that the degree of parasitaemia in naturally infected birds is low; even in those cases with an index above 100 erythrocytes parasitised per 10,000 examined, and with frequent polyparasitism, there were no signs of anaemia or mortality. Inoculations of cortisone, splenectomy, or a combination of both, are ineffective as methods of aggravating the pathogenicity of P. nettionis.