Prevalance and intensity of Haemoproteus columbae in domestic pigeons

Abstract

Haemoproteus columbae is a red-blood cell protozoon parasite of pigeons and doves. The pathogenicity of H. columbae is generally low and adult birds usually show no evidence of disease (Soulsby, 1986; Rommel et al., 2000). However, an acute form of the infection-has been reported in pigeon nestlings, in which heavy mortality has been recorded (Soulsby, loc. cit.). The frequency of H. columbae is considerably high in. pigeons worldwide (Mushi et al., 2000). There are very limited number of studies on blood parasites of pigeons in Turkey (Gulanber et al., 2002). This study was therefore designed to determine the prevalence and intensity of this parasite in domestic pigeons fro m Bursa region, Turkey during a one year period. Materials and Methods In this:study, one hundred (31 young 69 adult, 45 male, 55 female) domestic pigeons reared in pigeon houses in 10 districts of Bursa, Turkey were exmined for blood parasites between April 2002 and March 2003. Blood samples were obtained from the right wing vein and thin smears in duplicate were made immediately. The air dried blood smears were subsequently fixed with methanol and stained with Giemsa solution (5%, pH 7.2). The slides were examined microscopically at a magnification of x1000. Intensity was expressed as the number of parasitized red blood cells per 200 randomly selected fields. The parasite species was identified as described by Bennett and Peirce (1990). Chi-square or Fisher's exact was used to compare the prevalence of the parasite I among the age, sex and season groups. All statistical calculations were performed using the Graphpad Instat software V2.02. programme (LSU Medical Center). Results and Discussion In this study H. columbae was the only haemoparasite, with a prevalence of 21 per cent, found in blood smears of the pigeons examined. This rate is much lower than the prevalence. rates reported. In Turkey (Gicik, 2001; Gulanber et al., 2002.) and other countries (Mushi et al. and Sol et al., 2000) in domestic or wild pigeons. The low prevalence of H. columbae in pigeons in this study might be due to the different abundance of vectors in the habitats of domestic pigeons or due to a possible difference in susceptibility. Although-higher prevalence was observed in young pigeons (25.8%) compared to adult pigeons (18.8%) there was no significant difference between the age classes. Sol at al. (loc. cit.) and Gicik (,loc. cit.) found higher prevalence of H. columbae in adult pigeons than in youngs. No difference in the prevalence of H. columbae could be found between males (20%) and females (21.8%). Gicik (loc. cit.) found higher prevalence of H. columbae in wild female pigeons than in males, while. in their study Sol at al. (loc. cit.) stated that there is no difference between male and female in prevalence of H. columbae. Because prevalence largely depends on exposure to vectors, in our. study the absence of sex-related differences in prevalence suggests that the sexes were equally exposed to vectors. This agrees with the fact that, in pigeons, both sexes use the habitat in the breeding duties in a similar fashion. The highest (44%) infection rate was observed in autumn (P<0.05, n:27) months. and lowest (12 %) in spring (n:25) and summer (n:25) months; it was 13 % in winter (n:23) months. The highest proportion of youngs with incomplete immunity. in examined pigeons in autumn months may be the causative factor of this situation. This result is in agreement with the study of Klei and Deguisti (1975), who found that the highest infection rates with H. columbae in feral pigeons were observed in autumn and winter months. The intensity of parasitaemia in infected pigeons differed between 1-732 infected cells per 200 fields. The intensity of H. columbae in positive blood smears were as follows: 1-50 infected cells in 52.4%, 51 -100 infected cells in 4.8 %, 101 200 infected cells in 19% and 201-300 infected cells in 19%. Only 4.8% of the positive samples had more than 500 infected cells. Mean intensity of H. columbae in adults was lower than that in youngs. The lower parasite intensity in adults is to be expected if older birds acquire a certain degree of immunity against the parasite. In this study the similarity in the intensity between males and females can mean that both sexes are equally susceptible to parasite H. columbae.