Q fever is a main zoonotic disease around the world. The aim of this meta-analysis was to estimate the overall seroprevalence of Coxiella burnetii among human and animal population in Iran. Major national and international databases were searched from 2005 up to August 2016. We extracted the prevalence of Q fever antibodies (IgG) as the main primary outcome. We reported the prevalence of the seropositivity as point and 95% confidence intervals. The overall seroprevalence of IgG phase I and II antibodies of Q fever in human was 19. 80% (95% CI: 16. 35–23. 25%) and 32. 86% (95% CI: 23. 80–41. 92%), respectively. The herd and individual prevalence of C. burnetii antibody in goat were 93. 42% (95% CI: 80. 23–100. 00) and 31. 97% (95% CI: 20. 96–42. 98%), respectively. The herd and individual prevalence of Q fever antibody in sheep' s were 96. 07% (95% CI: 89. 11–100. 00%) and 24. 66% (95% CI: 19. 81–29. 51%), respectively. The herd and individual prevalence of C. burnetii antibody in cattle were 41. 37% (95% CI: 17. 88–64. 86%) and 13. 30% (95% CI: 2. 98–23. 62%), respectively. Individual seropositivity of Q fever in camel and dog were 28. 26% (95% CI: 21. 47–35. 05) and 0. 55% (0. 03–2. 68), respectively. Seroprevalence of Q fever among human and domestic animals is considerable. Preventative planning and control of C. burnetii infections in Iran is necessary. Active surveillance and further research studies are recommended, to more clearly define the epidemiology and importance of C. burnetii infections in animals and people in Iran.
Q fever is a zoonosis caused by the intracellular, gram negative bacterium Coxiella burnetii. C. burnetii is an extremely infectious pathogen [1]. The extremely high infectivity, the ability to withstand harsh environmental conditions, and the potential to cause severe disease in man, has deemed this organism to be considered as a biological terrorist agent. It has been listed as a Category B biological warfare agent by the Centre’s of Disease Control and Prevention [2,3]. C. burnetii infects people and a wide range of wild and domesticated animals. Within the environment, C. burnetii survives in arthropod hosts, such as ticks. From these hosts it can spread, and it primarily spreads into ruminants. Domestic ruminants (primarily cattle, sheep and goats) are the most important reservoir of C. burnetii in the nature. Q fever is mostly asymptomatic in livestock and animals, except in some cases, where causes abortion, stillbirth, endometritis or infertility. Infected animals shed C. burnetii into the environment in milk, colostrum, urine, vaginal discharges and especially in birth products [4,5]. High numbers of organisms exist in the amniotic fluids and placenta during birthing (e. g. , 109 bacteria/g placenta) [6]. C. burnetii can survive for long periods in the environment, and it is common for aerosols from infected herds to be carried by the wind and cause infection in humans. Q fever outbreaks could be directly connected to the speed and frequency of the wind [7]. Inhalation of infectious aerosol or contaminated dusts containing air-borne bacterium the major route of acquiring the disease in humans, so that a single inhaled organism may produce clinical illness. Nevertheless, the other routes of transmission of this infection to human are consumption of contaminated milks and dairy products, skin or mucosal contact, tick bites, blood transfusion, sexual transmission and embryo transfer [4,5, 8]. Clinical manifestations of Q fever in humans includes acute, chronic to fatigue syndrome. The main characteristic of Q fever is its clinical polymorphism. Acute Q fever is defined as primary infection with C. burnetii, and <60% of infected patients may be asymptomatic [9]. However, acute Q fever can manifest as a flu-like and self-limited illness, and major clinical presentations of these patients are fever, headache, coughing, atypical pneumonia, hepatitis, myalgia, arthralgia, cardiac involvement, skin rash and neurologic signs, and 2% of patients with acute disease are hospitalized. The case fatality rate of acute Q fever is reported up to 1–2% [4,8, 10]. Approximately 5% of acute Q fever cases go on to develop chronic Q fever. People may become chronically infected without having being previously diagnosed with acute disease, and chronic Q fever may manifest months or years after an acute infection [11]. Chronic Q fever is accompanied with endocarditis, vascular infection, prosthetic joint arthritis, osteoarticular infection and lymphadenitis [4,12,13]. Endocarditis and vascular infection caused by Q fever are fatal if untreated[9]. Human Q fever has been described in countries around the world, New Zealand being the only exception. As it is not a notifiable disease in many countries, the geographical distribution of the organism is extrapolated from serological surveys and investigated outbreaks[3]. In Iran, the first clinical cases of acute Q fever are reported in 1952. From 1970 to 1976,133 patients with acute Q fever were reported from different parts of Iran [14]. After 1976, Q fever was neglected in Iran, and no human case was reported. At the same time with large outbreak of Q fever in the Netherlands (2007–2010) [15], C. burnetii antibodies were reported in febrile patients in the Kerman province (southeastern Iran), [16]and investigation for Q fever was resumed. After that, various seroepidemiological studies were conducted on animal and human population. The first case of chronic Q fever (endocarditis) was reported in 2013 [17]. We do not have an overall estimation of Q fever infection in Iran. Current studies have reported Q fever seroprevalence in human and domestic animals. The overall estimation of Q fever seroprevalence in the human and animal population will help health policymakers create or modify control and prevention programs for Q fever in Iran. In the present systematic review, we reviewed the local Iranian publications on Q fever and also international publications relating to the disease in Iran. In this report we provide a summary of the more recent data collected on Q fever in Iran.
From January 2005 to June 2016, we searched the literature for articles that assessed the prevalence of Q fever infection in human and animals in Iran. We searched multiple English and Persian electronic data sources including Iranmedex, Scientific Information Database (SID), Magiran, Iranian Research Institute for Information Science and Technology (IRANDOC), Google Scholar, Medline, PubMed, Science Direct, Scopus and Web of science. In addition, the citations of the included articles were reviewed to find other relevant studies. We also looked at the electronic abstract list of congress conducted in Iran and also at the electronic database of students’ thesis. Keywords that we used for our search were “Q fever, Coxiella burnetii and Iran" . Articles with cross sectional design which were sampling from Iran, published in Persian or English and measured seroposivity by serological assays (just IgG) were eligible to enter meta-analysis. Exclusion criteria for studies from systematic review were: 1- Lack of access to full article or insufficient data in abstract; 2- Unclear testing methods used to detect studied infection or non-serology test 3- IgM detection4- other study design except cross sectional. We contacted the corresponding author when we have questions about the eligibility of the article. Data was extracted by two reviewers and checked twice based on the following items: type of study, sample size, location and time of the study, species and prevalence of Q fever. We grouped the studies with species in herd and individual level as sheep, goat, cattle and camel and also human participants as phase I and phase II IgG. We conducted meta-analyses in STATA version 12. We did meta-analysis for Q fever prevalence in any species in herd and individual level and in phase I and II for human. The outcome was measured and reported as prevalence, with point and 95% confidence intervals. A Q-test was used to assess heterogeneity. When the heterogeneity test had a p-value less than 0. 1, a random-effects model was used; otherwise the fixed-effects model was used to calculate the pooled prevalence. Also by calculating pooled Q fever seroprevalence in each province we mapped prevalence of Q fever using ArcGIS ver. 10. 2.
As presented in Fig 1, we found 163 abstracts in our literature review. After removing duplications (n = 87) based on title and abstract, 76 remained for full text review. Of those, 48 articles were excluded for various reasons including non-serology test (n = 34), review article (n = 7), IgM assessing study (n = 1), publish of Q fever study of other country in Iranian journals (n = 3), other kind of study (n = 2) and no access to full text (n = 1) (Fig 1). Characteristics of the final included studies (n = 28) in the systematic review showed in Table 1.
Not applicable. Not applicable.
Q fever is a zoonotic diseases caused by a bacterium so called Coxiella burnetii. Domestic ruminants (primarily cattle, sheep and goats) are the most important reservoir of C. burnetii in the nature. Q fever is mostly asymptomatic in livestock and animals. Clinical manifestations of Q fever in humans includes asymptomatic, acute, chronic to fatigue syndrome. Acute Q fever is defined as primary infection with C. burnetii, and <60% of infected patients may be asymptomatic. Acute Q fever can manifest as a flu-like and self-limited illness. Chronic Q fever is accompanied with endocarditis and vascular infection which is fatal if untreated. The results of this meta-analysis showed the prevalence of IgG phase I and II antibodies of C. burnetii among human in Iran were 19. 80% and 32. 86%, respectively. The prevalence of Q fever antibodies in cattle, goat and sheep were 13. 30%, 31. 97% and 24. 66% in Iran, respectively. Seroprevalence of Q fever among human and domestic animals is considerable. Preventative planning and control of C. burnetii infections in Iran is necessary. Active surveillance and further research studies are recommended, to more clearly define the epidemiology and importance of C. burnetii infections in animals and people in Iran.
livestock
medicine and health sciences
pathology and laboratory medicine
ruminants
pathogens
population dynamics
geographical locations
microbiology
vertebrates
animals
mammals
bacterial diseases
population biology
bacterial pathogens
coxiella burnetii
infectious diseases
sheep
medical microbiology
microbial pathogens
goats
iran
agriculture
people and places
asia
biology and life sciences
cattle
amniotes
bovines
q fever
organisms
geographic distribution
Seroprevalence of Q fever among human and animal in Iran; A systematic review and meta-analysis