Date Published: February 19, 2019
Publisher: Public Library of Science
Author(s): Ehsan Mostafavi, Leila Molaeipoor, Saber Esmaeili, Ahmad Ghasemi, Maedeh Kamalizad, Manijeh Yousefi Behzadi, Razi Naserifar, Mehdi Rohani, Abdolrazagh Hashemi Shahraki, Ulrike Gertrud Munderloh.
Q fever is a zoonotic disease of great public health importance in Iran. This disease is presented with high phase I antibody development in chronic and high phase II antibody in the acute form of illness. This study was conducted to evaluate the seroprevalence of Q fever among high-risk occupations in the Ilam province in Western Iran.
In this cross-sectional study, 367 sera samples were collected from five groups comprised of animal husbandry workers, farmers, butchers, slaughterhouse workers, and park rangers. The collected sera were tested for IgG antibodies against Coxiella burnetii using ELISA. The seroprevalence of antibodies against C. burnetii in phase I and II was 24.38% and 26.37%, respectively (i.e., 32.42% overall). Low educational level, living in rural areas, keeping sheep/goats, ages older than 50 years, and a history of arthropod bites positively correlated with increased risk of Q fever infection. Animal husbandry workers (45.13%) were at higher risk of contracting Q fever compared with other occupations in the study (17.11%).
High seroprevalence of C. burnetii among high-risk occupations is a serious challenge in the Ilam province. In addition, the high seroprevalence of endemic Q fever in rural and nomadic areas and a higher concentration of occupations who are directly engaged with livestock demonstrate the critical need for preventive medicine education and training in regards to mitigating risk for disease contraction in susceptible groups.
Q fever is a zoonotic disease caused by Coxiella burnetii  that has been reported from almost all over the world . Domestic ruminants such as cattle, sheep, and goats are the main reservoirs of the disease [3, 4]. Transmission of only a few bacteria is sufficient to cause infection . Humans are primarily infected via the respiratory route after inhaling aerosols and dust particles contaminated with C. burnetii. Contact with the infected placenta and birth products can have a significant role in the transmission of this agent . Consumption of raw milk and other unpasteurized dairy products, as well as bites of arthropods such as ticks, are less important transmission routes [2, 3]. With its high pathogenicity and resistance to drying and heat, the organism has been modified for the use as a bioweapon. Moreover, it is of significant importance as an agent of bioterrorism . The acute infection in humans is presented after 14 to 39 days of latent phase with nonspecific and variable symptoms ranging from an asymptomatic and self-limiting infection with fatigue, headache, fever, chills, and myalgia to atypical pneumonia or hepatitis. The chronic form of the disease can occur in 1–2% of patients as endocarditis, osteomyelitis, aseptic meningitis, and possibly others [6, 7].
In this study, 367 serum samples were taken from five groups, determined as occupations exposed to the risk of Q fever infection, including animal husbandry workers (n = 113), farmers (n = 82), butchers and slaughterhouse workers (n = 61), park rangers (n = 35), and those who referred to the laboratories (n = 76) in three cities of Ilam, Dehloran, and Mehran. Out of all studied cases, 76.29% (n = 280) were male, 89.86% (n = 328) were married. Also, 45.18% (n = 164), 44.08% (n = 160), and 10.74% (n = 39) were living in urban, rural, and nomadic areas, respectively (S1 File). The mean (± SD) age of the tested subjects was 40.54 (±13.55) years old ranging from 18 to 78 years of age.
In this study, the seroprevalence of antibodies against C. burnetii was investigated in high-risk populations in the Ilam province in the west of Iran. The seroprevalence of IgG antibody against phases I and II of the disease was 24.38 and 26.37%, respectively, with 32.42% as the overall seroprevalence. Previous studies conducted in Iran demonstrated similar results. For example, in a study conducted in Sistan and Baluchistan, in the southeast of Iran, the risk among slaughterhouse workers and butchers was examined and found that the seroprevalence of Q fever was 22.5% in 2016 . In another study in Kurdistan province, west of Iran, the seroprevalence of C. burnetii was reported 27.83% among hunters and their family members, butchers, the staff of public health centers, and patients who referred to laboratories . Moreover, studies conducted in the neighboring (west and northeast) countries of Iran have also reported high seroprevalence of Q fever. In two studies conducted in Turkey, the seroprevalence of Q fever among high-risk occupations and blood donors was 50.9% and 35.1%, respectively. The highest prevalence rates were detected in abattoir workers, butchers, and farmers (32.8%) [14, 31]. Another study in rural areas of Azerbaijan showed that the seroprevalence of Q fever was 60.2%. Risk factors associated with Q fever seropositivity were age, contact with goats, cats, and rodents, and mosquito bites . Also, the IgG antibody of C. burnetii was detected in 20% of aborted women in Iraq . However, it seems that the higher seroprevalence of this disease in the Ilam province is related to the economic activities of people who are mainly engaged in holding livestock and farming, which lead to more exposure to livestock. Exposure to domestic animals is considered to be a crucial risk factor in the dissemination of C. burnetii among human populations [10, 15]. The main route of infection is often inhalation of contaminated dust from infected animal feces, urine, milk and birth products . The most significant animal reservoirs for human infection seems to be associated with farms and include livestock such as cattle, goats, and sheep . The latter populations are believed to be the main reservoirs for urban outbreaks of Q fever [28, 34]. The results of this study, which concur with those published from other studies, have also demonstrated that the risk of Q fever infection in rural and nomadic areas, which have greater exposure to livestock, were 2 and 5.7 folds more than urban areas, respectively . The risk of seropositive cases among animal husbandry workers was 4 folds more than the controls (those who referred to the laboratories). Furthermore, our results also revealed that the risk of seropositive status of Q fever among those who were keeping animals was higher than those who were not keeping any animals (OR = 2.12, 95% CI: 1.31–3.43; p-value = 0.002); and among those who kept sheep or goats had a higher risk (OR = 7.67, 95% CI: 1.75–33.61; p-value = 0.007). Hence, to the best of our knowledge and according to the results of this study, more attention should be paid to a high seroprevalence of Q fever in rural and nomadic areas and occupations that are directly engaged with livestock.