Trop Anim Health Prod (2012) 44:1841–1846 DOI 10.1007/s11250-012-0146-9
ORIGINAL RESEARCH
Prevalence and risk factors associated with Chlamydophila abortus infection in dairy herds in Jordan Abdelsalam Q. Talafha & Mohammed M. Ababneh & Mustafa M. Ababneh & Ahmad M. Al-Majali
Accepted: 27 March 2012 / Published online: 13 April 2012 # Springer Science+Business Media B.V. 2012
Abstract A cross-sectional study was carried out to determine seroprevalence and to identify risk factors associated with Chlamydophila abortus infection in 62 nonvaccinated dairy herds (671 cows) in Jordan between January and June 2007. Information regarding herd management was recorded through a personal interview with farmers. Antibodies against C. abortus were detected using an ELISA test kit. Chi-square analysis and multivariable logistic regression model were used to identify risk factors associated with C. abortus seropositivity. The true prevalence of antibodies against C. abortus in individual cows and cattle herds were 19.9 % and 66.3 %, respectively. Univariable Chi-square analysis revealed three variables with P≤0.25 that were further offered to multivariable logistic regression analysis. Small-sized herds were identified as a risk factor for seropositivity to C. abortus, while sweeping followed by water hosing and using disinfectants were identified as protective factors. Cows in the age groups of >8 and ≤10 years old and >2 and ≤6 years old had the highest and lowest significant seroprevalence to C. abortus, respectively. Results of this study indicated that C. abortus is highly prevalent in Jordan's dairy herds and Chlamydophila infection could be controlled by applying strict biosecurity measures in the dairy farms. A. Q. Talafha (*) : M. M. Ababneh : A. M. Al-Majali Department of Veterinary Clinical Sciences, Faculty of Veterinary Medicine, Jordan University of Science and Technology, Irbid 22110, Jordan e-mail:
[email protected] M. M. Ababneh Department of Basic Veterinary Medical Sciences, Faculty of Veterinary Medicine, Jordan University of Science and Technology, Irbid 22110, Jordan
Keywords Chlamydophila abortus . Jordan . Risk factors . Seroprevalence
Introduction The Chlamydiaceae family consists of nine species grouped within two genera, Chlamydia and Chlamydophila (Everett 2000). Bacteria in this family are obligate, intracellular, Gram-negative parasites that multiply within the cytoplasm of the host cell (Kemmerling et al. 2009). Chlamydophila psittaci (formerly Chlamydia psittaci) pathogen for birds and Chlamydophila abortus (formerly Chlamydia psittaci serotype 1) pathogen for ruminants are the most important and best documented species in the Chlamydophila genus (Rodolakis and Yousef Mohamad 2010). They pose a zoonotic risk inducing mild influenza-like illness and, in rare cases, severe chlamydiosis characterized by pneumonia, endocarditis, encephalitis, abortion, and death to mainly pregnant women, handling sheep and goats (Longbottom and Coulter 2003). In cattle, acute infection with Chlamydophila species has been associated with a wide range of diseases including pneumonia, polyarthritis, polyserositis, conjunctivitis, encephalomyelitis, mastitis, and reproductive disorders including endometritis, salpingitis, vaginitis, abortion, repeat breeding, seminal vesiculitis, and epididymitis (Kaltenboeck et al. 2005; Kauffold et al. 2007; Yaeger and Holler 2007). However, the majority of Chlamydophila infections are not associated with obvious clinical signs (Biesenkamp-Uhe et al. 2007; Reinhold et al. 2008). In sheep and goats, C. abortus is known to cause ovine enzootic abortion. A wide variety of other vertebrates can be affected by chlamydiosis (Everett et al. 1999). Diseases caused by the Chlamydiaceae family were reported worldwide
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(Kaltenboeck et al. 2005) including tropical countries such as Namibia (Samkange et al. 2010) and India (Mani et al. 2011). The bacteria are shed in nasal secretions, feces, urine, vaginal discharge, placental membranes, and saliva. Animals acquire the infection through the respiratory, ocular, or oral routes. In utero infection and venereal transmission through infected semen or after mating of infected females are also possible in ruminants (Longbottom and Coulter 2003). Inhalation of infected aerosol is the most common route of transmission from animals to humans (Rodolakis and Yousef Mohamad 2010). Birds are considered excellent vectors for the maintenance of chlamydial infection in ruminants, since they feed on and have access to the secretions of infected animals (Everett et al. 1999). Knowledge of herd management and factors that increase the risk of C. abortus infection would improve our ability to control and prevent transmission, thereby minimizing adverse effects of chlamydial infection on herd health and productivity. The success of the control programs depends on the quality and effectiveness of available diagnostic tests. Definitive diagnosis of Chlamydia species requires either identification of the bacteria by microscopic examination of stained smears, detection of bacterial antigen by immunofluoresence or by ELISA, or detection of the bacterial DNA by polymerase chain reaction (PCR) or by microarray (Sachse et al. 2005; Rodolakis and Yousef Mohamad 2010). Complement fixation test is considered the standard serological test for detection of chlamydial antibodies by the Organisation Internationale des Epizooties (OIE) (http:// www.oie.int). However, the test lacks specificity in ruminants due mainly to its heat-resistant lipopolysaccharide (LPS) antigen which is common to all Chlamydiaceae species (Salinas et al. 2009). Several ELISA tests using purified whole elementary bodies (EB), LPS, or C. abortus major outer membrane protein (MOMP) improved sensitivity and specificity to detect antibodies against C. abortus (Travnicek et al. 2003; Niemczuk 2005; Rodolakis and Yousef Mohamad 2010). Because of a high local demand for dairy products for consumption in Jordan and support for dairy cattle development from the government, the dairy cattle population has been increasing during the last few years. As of November 2009, there were approximately 65,520 dairy cows in Jordan (DOS 2009). Ninety-two percent of the cows were Holstein-Friesian, while the rest were of the Baladi and Shami breeds (about 4 % each). The chlamydial infection status of Jordan's dairy herds has not been previously investigated. The aims of this study were to determine the individual and herd seroprevalence of C. abortus infection in nonvaccinated dairy cattle in Jordan and to determine potential risk factors related to seropositivity of dairy cattle herds.
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Materials and methods Study design A cross-sectional study was carried out between January and June 2007. Sample size was calculated using C-survey software 2.0 (UCLA, Los Angeles, CA, USA), with an expected prevalence of 10 %, confidence interval of 98 %, and percent of accepted error of ±4. The resulting sample size was adjusted to the cattle population in Jordan. A total of 671 cows were sampled from 62 herds from all over the country. The number of cows sampled from each governorate depended on the density of cows in that governorate. Herds were selected randomly using the records of the Jordanian Ministry of Agriculture. Cows from each herd were selected randomly using a table of random digits. Only female cows over 1-year-old were bled to avoid crossreactions with colostral antibodies. Herds were stratified into three herd size strata: small (150 cows). Balqa and Tafila governorates had small-sized herds; Madaba, Irbid, Mafrak, Jarash, Ajloun, and Karak governorates had medium-sized herds, while Amman and Zarqa governorates had largesized herds (DOS 2009). On the day of sample collection, each farmer was interviewed by the principal investigator using a pretested structured questionnaire (written in Arabic language and available from the corresponding author upon request) to collect information about farm characteristics and herd management. Collected information included herd size (26 small, 23 medium, and 13 large herds), vaccination history (yes, no), presence of regular veterinary services (yes, no), usage of disinfectants in farm cleaning (yes, no), cleaning method (not practiced, sweeping, sweeping and hosing), farm workers visiting neighboring farms (yes, no), source of feed (mixed in farm, bought from market), source of water (well, tap water), isolation of newly purchased animals (yes, no), presence of calving pens (yes, no), and abortion rate (more or less than 5 % per year). It is worth mentioning that cattle vaccination against C. abortus in Jordan is not practiced. All cattle were kept in open stalls with fence line separation between heifers and adult cows. The calves were housed separately until they were 3–4 months old. The cows were milked twice a day. All herds were vaccinated against foot-and-mouth disease, enterotoxemia, and anthrax. No other vaccines were used. All herds used anthelmintic medications on a regular basis. Sample collection Blood samples (10 ml) were collected from the coccygeal vein of each animal, using disposable needles and plain
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were offered to multivariable logistic regression analysis. All analysis was done using the statistical software package SPSS 17.0 2009 (SPSS Inc., Chicago, IL, USA).
vacutainer tubes (Occidem Biotech®, Middlesex, UK), and transported on ice to the laboratory. The samples were centrifuged at 5,000×g for 10 min to obtain the serum. Sera were stored in identified vials at −20°C until testing.
Results
Laboratory analysis
Seroprevalence of C. abortus
Serum samples were tested for antibodies against C. abortus with an enzyme-linked immunosorbent assay kit (The CHEKIT C. abortus antibody ELISA test kit®, IDEXX Laboratories, Westbrook, Maine, USA) according to the manufacturer's instructions. The sensitivity and specificity of the test are 95 % and 100 %, respectively. The resulting prevalence was adjusted to the test sensitivity and specificity using the formula published by Noordhuizen et al (1997).
One hundred and twenty-seven (18.9 %) serum samples out of the 671 examined sera were C. abortus seropositive. The true individual seroprevalence as adjusted to the test sensitivity and specificity was 19.9 %. Out of 62 studied cattle herds, 39 (63 %) had at least one seropositive cow. When adjusted to the test sensitivity and specificity, the true herd seroprevalence was 66.3 % (Table 1). Cows in the age groups of >8 and ≤10 years old and >2 and ≤6 years old had the highest and lowest significant seroprevalence (χ2; P8 and ≤10 years old and >2 and ≤6 years old had the highest and lowest significant seroprevalence (χ2; P0.05) and fluctuated from 58.7 % (1-yearold dogs) to 66.7 % in puppies. Moreover, there was no significant association between the nature of the clinical signs occurring during chlamydiosis and the age classes. The seroprevalence of C. abortus in cattle in Balqa and Tafila governorates of Jordan was significantly higher than that found in other governorates. In these two governorates, it was noticed that pigeons and chicken were raised in the dairy farms with free access of birds to cow's feed and water supply. It has been reported that Chlamydia psittaci, Chlamydophila pneumonia and C. abortus can be found in the fecal material and respiratory exudates of infected birds which results in contamination of the environment and spread of the disease in cattle (Borel et al. 2006). Chlamydia psittaci serovars WC and B were associated with enteritis and abortion in cattle, respectively (Longbottom and Coulter 2003).
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freezing for weeks or even months (Hirsh and Biberstein 2004; Liutkeviciene et al. 2009). It has been reported that cleaning and disinfection of the pens, especially after parturition or abortion with proper herd management, such as isolation of affected animals and proper disposal of dead calves, placentas, and bedding; preventing access of birds to the feed and water supply of cows; and thoroughly washing hands after dealing with infective material, before tending other animals, are essential measures to limit the risk of spreading contamination (Longbottom and Coulter 2003). Chlamydiae is susceptible to most disinfectants and detergents as well as to heat. One in 1,000 dilution of quaternary ammonium compounds, 70 % isopropyl alcohol, 1 % Lysol, one in 100 dilution of household bleach or chlorophenols are all effective (Longbottom and Coulter 2003). Factors, including presence of regular veterinary services, farm workers visiting neighboring farms, source of feed and water, isolation of newly purchased animals, presence of calving pens, and abortion rate were not significantly associated with seropositivity to C. abortus in this study.
Risk factors associated with seropositivity to C. abortus Three variables were significantly (P
