Seroprevalence of Q fever in farm animals in Saudi Arabia. Abdulrahman A. Jarelnabi 1 , Mohammed A. Alshaikh 1 , Amel O. Bakhiet 2 , Sawsan A. Omer 3 , Riyadh S. Aljumaah 1 , Gordon D Harkiss 4 , Osama B. Mohammed 5* , Mansour F. Hussein 1 1 Department of Animal Production, College of Food & Agricultural Sciences, King Saud University, Riyadh, Saudi Arabia 2 College of Veterinary Medicine, Sudan University of Science and Technology, Khartoum North, Sudan 3 Department of Zoology, College of Science, King Saudi University, University Centre for Women Students, Riyadh, Saudi Arabia 4 MV Diagnostics Ltd, Nine BioQuarter, Little France Road, Edinburgh EH16 4UX, UK 5 KSU Mammals Research Chair, Department of Zoology, College of Science, King Saudi University, Riyadh, Saudi Arabia Abstract This study was undertaken to determine the seroprevalence of Q fever in domestic livestock in Saudi Arabia. Serum samples from 489 camels, 428 cattle, 630 sheep and 423 goats, of either sex, from different localities were tested for antibodies against C. burnetii using a Q fever indirect enzyme-linked immunosorbent assay (ELISA). A subsample of 307 animals of different species was simultaneously tested for C. burnetii antibodies by ELISA and indirect immunofluorescence (IFA). The overall seroprevalence was 30.71%. Prevalence by species was 51.53%, 30.67%, 34.04% and 12.38% in camels, cattle, goats and sheep, respectively. Significant differences in seroprevalence were recorded between species and locations. The prevalence was overtly higher in adult as compared to young animals. No significant difference was recorded between male and female animals. There was a close agreement between ELISA and IFA results in cattle and camels while the results of the two tests were at variance in sheep and goats. The results indicate that the domestic livestock and the camel are the source of Q fever endemicity in Saudi Arabia. Keywords: Q fever, ELISA, Farm animals, IFA, Saudi Arabia, Seroprevalence. Accepted on November 27, 2017 Introduction Q fever (Coxiellosis) is a ubiquitous anthropozoonosis caused by Coxiella burnetii, an intracellular bacterium with a wide range of vertebrate and invertebrate hosts including man, domestic animals and birds [1]. The organism has been reported from all parts of the world, with the exception of the Antarctic region [2]. In nature, C. burnetii circulates between ticks and small wild mammals [3]. In humans and domestic animals, the infection is usually aero-genic, but could also be acquired by ingestion and other routes. C. burnetii is characterized by extremely high infectivity and resistance in the environment [4]. Following a long period of underestimation and misdiagnosis or undiagnosed [5,6], Q fever has recently re-emerged as a public health and veterinary problem in many countries. A major epidemic of Q fever affecting nearly 4,000 people has been reported during 2007-2010 in the Netherlands, in which infected dairy goats were identified as the most likely source of infection [7,8]. A multistate outbreak of human Q fever has also been reported recently in the USA [9]. The earliest reference to Q fever in Saudi Arabia dates to the 1960’s when the disease was first recognized as holo-endemic among the inhabitants of that country [10,11]. Over the next 50 years, three reports on human Q fever and two on Q fever in animals have been published. In humans, a single case of acute Q fever leading to meningoencephalitis was reported in a US soldier returning from Saudi Arabia after the first Gulf war [12], while asymptomatic infection was reported in four other soldiers, presumably after exposure to animals in that country [13]. More recently, 18 out of 51 persons in Saudi Arabia tested by immunofluorescence were positive to Q fever antibodies, but no information was available on their history or location [14]. A similarly striking paucity of information applies to Q fever in animals in Saudi Arabia, where only two reports are found in the literature, one on serological detection ISSN 0970-938X www.biomedres.info Biomed Res 2018 Volume 29 Issue 5 895 Biomedical Research 2018; 29 (5): 895-900