Serological Survey for Q-fever in Camels (Camelus dromedarius) in Riyadh Area, Kingdom of Saudi Arabia

Abstract

The primary objective of this study was to detect the presence of Coxiella burnetii infection in indigenous Saudi camels (Camelus dromedaries), to ascertain the prevalence of infection among these animals in Riyadh region, determine the effect of age, breed, sex, location and type of husbandry on prevalence and describe associated clinical manifestations, if any. During the tenure of the study, a small number of sheep and goats sharing the same habitat with the camels were also tested for coxiellosis. Furthermore, serological tests were conducted on some camels for Chlamydophilus abortus antibodies. Serum samples collected randomly from a total of 460 Saudi camels in Riyadh region were tested for antibodies against Coxiella burnetii using a competitive enzyme-linked immunosorbent assay. The animals comprised male and female camels of different age groups and breeds in five locations in the region. They also included housed and range camels. The results indicated 62% prevalence of C. burnetii antibodies in the sera of these animals. No significant differences were observed among the infected camels due to their age, sex, breed, location or type of husbandry, apart from a significant decrease in prevalence in relatively old XIII females. Some adult female camels were pregnant or lactating at the time of sampling but neither of these conditions was found to be associated with increased prevalence of C. burnetii. Furthermore, although some of the camels had clinical mastitis, the incidence of the latter was comparable in both C. burnetii-positive and C. burnetii-negative female camels. Ticks were found on both serologically positive and serologically negative camels of either sex but no attempt was made to investigate the role of ticks in transmitting coxiellosis to these animals. Examination of camels' sera for various biochemical and electrolyte parameters showed significantly higher total globulin and, hence, total protein values, in C. burnetii-positive as compared to C. burnetii-negative camels, suggesting increased immunological response in the former. The former camels also had higher creatinine and lower glucose values than the latter but no specific inferences could be made since the values of these two parameters in both groups of camels were still within normal ranges. Serological examination of 48 sheep and 44 goats kept alongside the camels revealed antibodies to C. burnetii in both species, with an overall prevalence of 70% and 27%, respectively. Hence, the possibility of cross-transmission between these animals and camels could not be ruled out. 186 camels were tested for Chlamydophilus abortus antibodies using competitive ELISA, with an overall prevalence of 19.4% being recorded. However, in contrast to coxiellosis, the prevalence of chlamydiosis was significantly higher in female (21%) than male (8.3%) camels and the vast majority of positive cases were adult animals. All serologically positive camels were clinically normal at the time of sampling. This is the first record of both coxiellosis and chlamydiosis in indigenous camels in Saudi Arabia. Further investigations should be undertaken to determine the prevalence of these infections on a countrywide basis and to elucidate the epidemiology and distribution of these diseases in the Kingdom, their clinical XIV importance as potential causes of infertility and mastitis in camels and their possible zoonotic impact.