Studies on Q Fever in Farm Animals in Kingdom of Saudi Arabia

Abstract

The serological prevalence of Coxiella burnetii in domestic livestock in Saudi Arabia was studied using two serological tests: indirect enzyme linked Immunosorbent assay (ELISA) as the main test and indirect immunofluorescence assay (IFA) as a confirmatory test and for .comparison with ELISA A total of 1970 farm animals of both sexes were tested serologically to determine the prevalence of C. burnetii specific IgG antibodies using indirect ELISA. The samples were collected from 489 camel, 428 cattle, 630 sheep and 423 goats. The animals were broadly divided into young and adult animals. All of them were clinically normal when sampled and .none of the adult females was pregnant while some were lactating A total of 605 animals had anti-C. burnetii IgG antibodies in their sera, giving an overall serological prevalence of Q fever of 30.71% with a mean ELISA titre (S/P ratio or O.D.%) of 103.03%. These results indicate that C. burnetii is common in all species a of farm animals in Saudi Arabia. Camels showed the highest proportion of Q fever (C. burnetii) positive sera among all the species tested, with an overall prevalence of 51.53%. The second highest serological prevalence was recorded in goats (34.04%), followed by cattle (30.61%) and the least in sheep (12.38%). In all species, the serological prevalence of anti-C. burnetii antibodies was significantly higher in adult compared to young animals (p<0.0001). Females animals tended to be more commonly affected than males; however, statistical analysis revealed non-significant inter-sex difference (p= 0.5847). Antibodies against C. burnetii in domestic livestock were also investigated using ELISA assay in 285 defatted milk samples obtained from 48 she-camels, 90 cows, 60 ewes and 87 does. Milk samples from 30 camels (62.5%), 30 cows (33.3%), 24 goats (27.6%) and ii 3 ewes (5%) were positive for anti-C. burnetii antibodies. Serum samples from the same animals were simultaneously tested by ELISA. Of these, 32 camels (66.66%), 38 cows (42.2), 13 goats (14.9%) and 4 ewes (6.67%) were positive for anti-C. burnetii antibodies. Statistical analysis show a significant correlation between ELISA results in milk and serum. Serum samples from a total of 307 animals, comprising 92 camels, 72 cows, 72 sheep and 71 goats, were also subjected simultaneously to indirect immuno-fluorescence (IFA) and ELISA assays. A statistically significant correlation was found between the serological prevalence of Q fever as determined by these two assays. Using ELISA as a reference serological test, statistical analysis showed that both the sensitivity and specificity of IFA assays were good, indicating that either ELISA or IFA can be used for screening Q fever in farm animals or as confirmatory tests to one another. The shedding of C. burnetii by serologically positive animals was investigated by the polymerase chain reaction (PCR), using primers that amplify the repetitive transposon-like region of C. burnetii. The study was conducted on 82 whole blood, 72 milk, 29 faecal and 21 urine samples collected from camels. In addition, 29 milk samples and 7 whole blood samples from cattle, 38 whole blood, 29 milk and 20 faecal samples from goats and 22 blood samples from sheep were available for .PCR analysis Out of a total of 149 whole blood samples collected from these different animal species, 13 samples (15.85%) from camels and 2 samples (5.6%) from goats showed positive amplification for C. burnetii DNA while all 22 sheep and 7 bovine blood samples were negative. Out of 144 milk samples collected from camels, cattle and goats, 5 samples (6.49%) from camels, 11 samples (28.94%) from cows and 0 samples from goats were positive for C. burnetii DNA. In addition, faecal samples collected from 29 camels and 20 goats revealed positive PCR products from 8 (27.59%) iii and 12 (60%) samples, respectively. C. burnetii DNA was also demonstrated in 5 (23.81%) out of the 21 urine samples collected from camels. All sampled subjected to PCR analysis were from serologically positive animals with the exception of urine samples which were collected from slaughtered camels that were not serologically tested for anti-C. burnetii antibodies. Serum samples from known Q fever-positive and known Q-fever negative animals were used to study the possible effects of Q fever on various biochemical and electrolyte parameters. A total of 281 serum samples were collected from camels, sheep, goats and cattle. In all species, no significant differences were found between Q-fever positive and Q-fever negative animals. However, a few intra-specific differences existed within each species. The effect of Q fever was also investigated in the levels of anti-oxidant enzymes, namely thiobarbituric acid reactive substances (TBARS) and reduced glutathione (GLUTH). TBARS level was determined in 239 known Q fever-positive and Q fever-negative animals while GLUTH level was determined in 188 known Q fever-positive and Q fever-negative animals. No significant differences in TBARS levels were found between Q fever-positive and Q fever negative animals in samples collected from each of goats, camels and sheep. However, the GLUTH level was found to be significantly reduced (p<0.002) in Q fever-positive camels as compared to Q fever negative camels. This enzyme is found in the cytoplasm of almost all mammalian cells, and a reduction in its activity could indicate some degree of cellular damage. However, further studies are needed to verify .this aspect This study constitutes the first record of C. burnetii in cattle, sheep and goats in Saudi Arabia and the second, and more detailed, study on camels .in the country