SEROPREVALENCE RATE OF COXIELLA BURNETII IN COWS’ SERUM IN ASSIUT GOVERNORATE, EGYPT

This study was conducted to determine the seroprevalence of Coxiella burnetii in cows from Assiut Governorate, Egypt. A total of 268 blood samples were collected from cows (176 females and 92 males). The age of these animals ranged between 2 months and more than 3 years. Screened for C. burnetii using indirect enzyme-linked immunosorbent assay. A total of 15.67% (42/268) was serologically positive. The seropositivity was high in females (19.56%) than males (13.63%). The native breed was more infected (17.44%) than Fresian (13.33%) and mixed ones (11.76%). In cows, a higher seroprevalence was observed in the age group more than 1 to 2 years (22.38%). Dairut city recorded the highest seroprevalence rate (40.74%) of C. burnetii . C. burnetii seroprevalence was higher in hot season (20.10%) than cold season (5.95%). Cows free from ticks recorded higher seroprevalence (22.58%) than those infested with ticks (12%). Cows with fever and pneumonia recorded higher seroprevalence (14.29%) compared to animals with other signs. In conclusion, findings of this study revealed the wide spread of C. burnetii infection among cows at Assiut Governorate, Egypt.


INTRODUCTION
Globally contagious zoonosis known as Q fever is carried on by the gram-negative, strictly intracellular bacteria Coxiella burnetiid (C. burnetii) (Woldehiwet, 2004). The absence of distinct clinical indications among infected livestock makes diagnosis difficult, and C. burnetii infection in livestock frequently goes undetected (Cutler et al., 2007). Q fever illness can occasionally lead to latestage abortions, stillbirths, or the delivery of fragile infants. However, there is no much efforts made to control this pathogen in animals, since it is not thought to cause economically significant animal disease (Maurin and Raoult, 1999).
Since the impact of Q fever has been recognized, serologic surveys have been carried out to determine the disease's prevalence in both humans and animals. Because the disease is difficult to isolate and doesn't grow on standard laboratory bacteriological media, culture of the disease is rarely performed (Kilic et al., 2005).
Numerous clinical and seroepidemiological studies were carried out in our area, suggesting that Q fever is a common illness in Egypt (Hussein, 1993;Mazyad and Hafez, 2007). Recently, there are a few data about this disease in cows in our community. Therefore, the current investigation was conducted to estimate the seroprevalence rate of C. burnetii in cows' serum in Assiut Governorate.

Sampling
The sample in this study was collected between March 2021 and February 2022.A sum of 268 blood samples were collected from cows (176 females and 92 males), which apparently appear healthy and diseased at Assiut Governorate. The age of these animals ranged between 2 months and more than 3 years in cows.
Five ml of blood was drawn from each animal via jugular vein puncture and collected on plain serum tubes for serological examination. Samples were transported in coolers to the Zoonosis laboratory, Faculty of Veterinary Medicine, Assiut University. The serum was separated within 24 hours after sampling. All sera were stored at -20°C for further investigation.

ELISA test
The animal sera were tested for the presence of specific anti-C. burnetii IgG antibodies using ELISA CHECKIT Q-fever test with a mixture of C. burnetii phases I and II, according to manufacture procedure (IDEXX Switzerland GmbH, Stations Strasse 12,CH-3097, The results were read using a photometer (Stat Fax-2100.Awareness, technology INC) at a wavelength of 450 nm.

Statistical analysis
The collected data were analyzed using computer program SPSS (Statistical Package for the Social Science) version 25. The data was subjected to analysis of variance using the Chi-square procedure of SPSS software. A probability value (P-Value) P < 0.05 was considered statistically significant.

DISCUSSION
Because of fever is now widely recognized for how important, and because it is rarely performed on culture due to the organism's inability to grow on standard laboratory bacteriological media, which necessitates a prolonged isolation period and biosafety level III conditions, serological surveys have been carried out to determine the disease's prevalence in both humans and animals (Kilic et al., 2005). The diagnosis of C. burnetii infection in both humans and animals can be made using a variety of techniques, however, previous studies reported that ELISA for serological inquiry and PCR for molecular detection of Coxiella DNA are the most effective methods (Hadush et al., 2016;Ullah et al., 2019).
As detected here, the seroprevalence rate is higher in female animals 19.56% (18/92) than male 13.63% (24/176) and the difference was statistically non-significant (P = 0.205) ( Table 1). Previous studies supported these findings in cattle, including studies from Laikipia, Kenya (Larson et al., 2019) and Northern Regions of Cameroon (Zangue et al., 2022). These findings are consistent with earlier findings that showed a higher frequency in females than in males. The increased susceptibility of pregnant cows and the constant release of organisms into the environment following normal parturition or abortion through the placenta, amniotic fluid, vaginal discharge, fetal membranes, and milk may be the causes of higher sero-activity in females (Sakhaee and Khalili, 2010).
As reported in the present study, higher seroprevalence of 22.38% was observed in cows in the age group more than 1 to 2 years, followed by 20.58% in the age group more than 3 years; while lower seroprevalences of 12.5% were detected in the age groups more than 2 to 3 years, followed by 11.97% in the age group between 2M and 1Year. Differences between age groups were statistically non-significant (P = 0.201) ( Table 2). Recent studies reported that the risk of getting C. burnetii infection among old animals (more than 1 year old) was 23 times higher than the risk among young animals (less than 1 year old) (Aljafar et al., 2020). Furthermore, animals aged between 6-9 years were recorded 1.89 times more likely to have been infected to C. burnetii (Zangue et al., 2022). The higher seroprevalence rates in the old animals may be attributed to more exposure to C. burnetii antibodies (Kiptanui et al., 2022).
As recorded in the current study, cows free from ticks recorded a higher seroprevalence rate (22.58%) than those infested with ticks (12%). The difference was statistically significant (P = 0.023) ( Table 4). This result may be due to continuous spraying of animals with insecticides to kill ticks., confirming the results previously reported in the Netherlands' outbreak, where ticks were detected to play no significant role in C. burnetii transmission (Sprong et al., 2012).
The present study revealed that C.burnetii seroprevalence in cows was higher in the hot season (20.10%) than in the cold season (5.95%). The difference was statistically significant (P = 0.003) ( Table 5). Higher detection of C. burnetiid in cows in the hot season in the current study may be due to increased stress on animals, which plays arole in decreasing animal immunity and tick spreading.
Higher seroprevalence rate of C. burnetii was detected in cows among the native breed (17.44%), followed by Fresian (13.33%) and mixed breed (11.76%), and the difference was statistically non-significant (P = 0.553) ( Table 6). This finding may be associated with genetics and exposure to the causative agent (Kiptanui et al., 2022), increasing the number of native breed animal samples in this study and lowering immunity of this breed than others. Moreover, the seroprevalence rate of C. burnetii was slightly higher in cows with clinical signs (16.12%) than those apparently healthy (15.61%) and the difference was statistically non-significant (P = 0.948) (Table7). This result may be due to the rarely appearance of Q fever signs in animals. Furthermore, cows with fever and pneumonia recorded a higher seroprevalence rate of C. burnetii (14.28% for both signs), compared to cows with other clinical signs (0%) (Table8). This finding confirmed that fever and pneumonia are the principal manifestations of Q fever in diseased animals (Marrie, 1995;Smit et al., 2012).

CONCLUSION
In comparison to other previous studies in Egypt, the findings of this study show a high seroprevalence of Q fever among diseased and apparently healthy cows. However, other animals and people in the study region may contract C. burnetii infections from these animals.