Epidemiological studies on caprine arthritis-encephalitis virus infection in Jordan

Small Ruminant Research 66 (2006) 181 186 Epidemiological studies on caprine arthritis-encephalitis virus infection in Jordan Khaled Al-Qudah, Ahmad M. Al-Majali, Zuhair Bani Ismail Department of Veterinary Clinical Sciences, Faculty of Veterinary Medicine, Jordan University of Science and Technology, P.O. Box 3030, Irbid 22110, Jordan Received 26 April 2005; received in revised form 17 August 2005; accepted 5 September 2005 Available online 24 October 2005 Abstract To investigate the seroprevalence of, and risk factors for, caprine arthritis-encephalitis virus (CAEV) infection in different breeds of goats in Jordan, sera from 1100 goats from three different geographical regions in Jordan were analyzed. Prevalence of antibodies to CAEV was determined using a competitive ELISA test. A semi-structured questionnaire was used to collect information on herd health and management. Questionnaire data were tested in a multivariable logistic regression model to elucidate risk factors associated with CAEV seropositivity. In addition, the incidence of CAEV antibodies was investigated in six goat herds located in the northern part of Jordan. Out of the 69 goat herds investigated, 16 (23.2%) had antibodies against CAEV. Individual goat true seroprevalence to CAEV was 8.9%. The highest CAEV seroprevalence was observed in goats older than 3-years and younger than 6-years of age. The seroprevalence of CAEV in goats was significantly higher (P < 0.05) in the northern part of Jordan than that in central or southern parts of Jordan. The multivariable logistic regression model identified large herd size (OD = 2.0; 95% CI: 1.1, 2.7), addition of new animals to the herd (OD = 1.3; 95% CI: 0.3, 1.6) and contact with other goat herds (OD = 1.1; 95% CI: 0.9, 2.0) as risk factors for CAEV seropositivity. The incidence of CAEV seropositivity in the six herds monitored in the northern part of Jordan ranged from 2.4 to 5.3%. 2005 Elsevier B.V. All rights reserved. Keywords: Goats; CAEV; Seroprevalence; Risk factors 1. Introduction Caprine arthritis-encephalitis virus (CAEV), a singlestranded, RNA virus of the family Retroviridae and the sub-family Lentivirinae, causes a persistent infection in goats (Knight and Jokinen, 1982; Pugh, 2002). There are five major clinical presentations associated with CAEV infection including polyarthritis, interstitial pneumonia, mastitis, and progressive weight loss in Corresponding author. Tel.: +962 2 7201000x22013; fax: +962 2 7095123. E-mail address: almajali@just.edu.jo (A.M. Al-Majali). adult goats, and encephalitis in younger kids (Smith and Sherman, 1994; Matthews, 1999; Pugh, 2002). However, most goats infected with CAEV become asymptomatic carriers. Viral transmission usually occurs horizontally through the ingestion of viral-infected goat milk and/or colostrums (Rowe et al., 1991, 1992; Rowe and East, 1997). Other potential sources of viral transmission include transmission in utero, contact with the vagina of an infected doe during parturition, via saliva or respiratory secretions, via contact with infected blood, viral contamination of milking equipment, needles, tattooing equipment, and breeding (Adams et al., 1983; Rowe et al., 1991, 1992; Rowe and East, 1997). 0921-4488/$ see front matter 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.smallrumres.2005.09.020

182 K. Al-Qudah et al. / Small Ruminant Research 66 (2006) 181 186 Since its documentation in goats in early 1970s, the disease has been reported worldwide. In Europe, the disease has been reported with a variable prevalence rate ranges from 12.1% (in Spain) to 56.8% (in Wales) (Houwers and van der Molen, 1987; Krieg and Peterhans, 1990; Cutlip et al., 1992; Greenwood et al., 1995; Literak et al., 1995; Contreras et al., 1998). In the Middle East, CAEV infection was reported in Saudi Arabia, Syria, and Turkey and the prevalence rates ranged from 0.8 to 12.5% (Alluwaimi et al., 1990; Giangaspero et al., 1992; Burgu et al., 1994). The purpose of this study was to document the presence and the prevalence of CAEV in different breeds of goats in Jordan and to elucidate risk factors associated with seropositivity to CAEV infection. 2. Materials and methods 2.1. CAEV serological survey 2.1.1. Studied animals A cross-sectional study with a multiple stage design was performed during the period between May 2001 and June 2003 to investigate the epidemiology of major infectious diseases affecting goat herds in Jordan. As a result of this cross sectional survey, recently, we have reported the epidemiology of caprine brucellosis in Jordan (Al-Majali, 2005). In this study, we have used the same materials (data and samples) to investigate the epidemiology of CAEV in Jordan. Sample size (1100 goats) was calculated using an expected prevalence of 5% and a confidence interval of 95% and then adjusted for the population size of goats in Jordan. To determine the number of goat herds to sample, the sample size (1100 goats) was divided by the number of animals to sample from each herd that will allow detecting at least one positive animal according to the equation published previously (Martin et al., 1987). Therefore, the number of goat herds to sample was 69. Equal number of herds was collected from three main geographical regions in Jordan (north, middle, and south). Herds and animals within each herd were selected by random sampling using a table of random digits. Only goats older than 8 months were sampled. Herds were stratified into three herd size strata: small herds (10 50 heads), medium herds (51 100 heads) and large herds (more than 100 heads). Farmers were asked to fill out a semi-structured questionnaire that contains information on herd size, breed, health status, and herd management. Information regarding herd management include, rearing system (categorized as intensive animals were kept most of the time indoors and fed manually at least twice per day and semi-intensive animals were kept indoors only at night and fed manually just once per day ), raising sheep in addition to goats, presence of regular veterinary service, contact with other goat herds, and addition of new animals. Both types of rearing systems (intensive and semi-intensive) are practiced in all the three studied geographical areas. 2.1.2. Sample collection Blood samples were collected from the external jugular vein aseptically, while restraining the animal in a standing position, using disposable needles and vacutainer tubes. After separation by centrifugation, serum was stored at 20 C until testing. 2.1.3. Sample analysis All collected sera were evaluated for anti-caev surface envelope (SU) antibodies using a commercially available competitive ELISA kit (celisa) (VMRD Inc., Pullman, WA, USA). This celisa kit utilizes 96-well microtiter plates coated with CAEV-63 SU captured by monoclonal antibodies (MAb) F7-299 and measures the displacement of horseradish peroxidase-conjugated MAb GPB74A binding by undiluted goat sera. The kit includes standard positive and negative control goat sera. The sensitivity and specificity of this celisa kit was previously investigated and were 100 and 96.4%, respectively (Herrmann et al., 2003). Anti-CAEV antibody titers were determined by estimating the end point celisa reactivity with two-fold or five-fold dilutions of goat sera. 2.2. Incidence of CAEV in goat herds from Northern Jordan Six goat herds located in the northern part of Jordan were monitored over a year period. Serum samples were collected from about 20% of the total number of goats in each herd. At time of sampling, goats were properly identified by ear tags. Sera were collected from the same goats from each herd in a 3-month interval. Owners of those six herds were asked to record any changes in herd management including new purchases. All collected sera were tested using celisa as described above. 2.3. Statistical analysis The true prevalence of serologically positive animals was estimated by adjusting the apparent prevalence to the sensitivity and specificity of the test using the following

equation (Rogan and Gladen, 1978): K. Al-Qudah et al. / Small Ruminant Research 66 (2006) 181 186 183 TP = AP + SP 1 Se + Sp 1 where TP is true prevalence, AP the apparent prevalence, Sp the test specificity, and Se is the test sensitivity. Univariable analysis was carried out by chi-square analysis. The effect of herd size, breed, health status, and management on CAEV seropositivity was assessed using a multivariable logistic regression model. All variables with P < 0.05 (two-sided) in the univariable analysis were further tested by the model. Variables were excluded from the model using a backward-stepwise approach. Statistical analyses were performed using SPSS software Version 10 (SPSS Inc., Chicago, IL, USA). 3. Results 3.1. CAEV serological survey Sixteen goat herds (23.2%) were found to have at least one serologically positive animal. One hundred thirty four goats (12.2%) out of the 1100 surveyed were seropositive to CAEV. The true prevalence of seropositive individual animals, as adjust to the specificity and sensitivity of the celisa test, was 8.9%. Within the 16 positive herds, the highest prevalence of seropositive animals was observed in goats older than 3-years and younger than 6-years of age (Table 1). Significant (P < 0.05) geographical variation in the prevalence of Fig. 1. Prevalence of antibodies to CAEV in sera of 1100 goats from northern, central, and southern parts of Jordan (2001 2003). (a and b) Seroprevalences with different letters differ (P < 0.05). seropositive herds was observed (Fig. 1). The highest CAEV seroprevalence occurred in the northern part of Jordan (55%). 3.2. Incidence of CAEV infection in northern Jordan Five out of the six goat herds that were included in the incidence study had at least one positive animal during the first sampling period. After the second sampling, all six herds had at least one positive animal. A total of 510 serum samples were collected during the 1-year observational period of these herds. The incidence of new cases per sampling time was ranged from 2.4 to 5.3% (Table 2). Table 1 Prevalence of CAEV seropositivity of goat herds from Jordan as stratified by age and sex Age (months) N Sex No. positive Prevalence Male Female 8 36 332 30 302 28 8.4 37 60 407 10 397 61 15.0 a 61 72 237 47 190 33 13.9 a More than 72 124 38 86 12 9.7 a Statistically significant. Table 2 Incidence of CAEV seropositivity of six goat herds from the Northern part of Jordan Herds 1 2 3 4 5 6 Total number of goats in herd 102 98 83 204 152 67 Number of goats sampled 21 19 17 41 30 13 Number of times sampled 4 4 4 3 4 3 Incidence of CAE 5.3 4.8 4.1 3.7 3.2 2.4

184 K. Al-Qudah et al. / Small Ruminant Research 66 (2006) 181 186 Table 3 Univariable analysis of seropositivity to CAEV by celisa with respect to different exposure factors Factor Category N CAEV celisa P a No. positive No. negative Herd size Small 30 5 25 0.031 Medium 21 4 17 Large 18 7 11 Rearing system Intensive 21 5 13 0.31 Semi-intensive 48 11 40 Presence of sheep Yes 24 7 17 0.5 No 45 9 36 Addition of new animals Yes 37 11 26 0.03 No 32 5 27 Contact with other goats Yes 37 10 27 0.02 No 32 6 26 Usage of disinfectants Yes 39 9 30 0.41 No 30 7 23 Veterinary service Yes 29 7 22 0.34 No 40 9 31 Breed Shami 26 8 18 0.04 Baladi 21 4 17 Mixed 22 4 18 a P-values are for comparisons of data for each factor evaluated. Higher incidence (P < 0.05) occurred directly after the end of the kidding season (October January). Most of the new seropositive cases (58%) were in kids less than 2 months of age. The incidence rate remained constant for five of the six herds. In one herd, the incidence rate increased after the first sampling time. 3.3. Multivariable logistic analysis The different studied variables were distributed among goat herds that were CAEV seropositive (Table 3). Four variables had P(χ 2 ) < 0.05 and were further evaluated using the multivariable logistic regression model. The model revealed three statistically significant (P < 0.05) risk factors (large herd size, addition of new Table 4 Logistic regression analysis of variables associated with goat herd seropositivity to CAEV in Jordan Variable b S.E. OR 95% CI OR P Constant 1.2 0.10 0.004 Large herd size 0.5 0.08 2.0 1.1, 2.7 0.03 Adding new animals 1.5 0.25 1.3 0.3, 1.6 0.04 Contact with other 1.7 0.27 1.1 0.9, 2.0 0.05 goat herds Likelihood ratio of chi square (LR χ 2 ): 112 on 12 degrees of freedom. animals and contact with other goat herds) for CAEV seropositivity (Table 4). 4. Discussion This study is the first to investigate the epidemiology of CAEV infection in different breeds of goats in Jordan. Herd seroprevalence in this study (23.2%) was higher than that reported in Turkey (1.9%), southern Mexico (3.6%), and Great Britain (10.3%) (Dawson and Wilesmith, 1985; Burgu et al., 1994; Torres-Acosta et al., 2003). On the other hand, the herd prevalence reported in this study was lower than that reported in Central Mexico (28.6%), Wales (56.8%), Australia (82%), and USA (73%) (Adams et al., 1984; Grewal et al., 1986; Cutlip et al., 1992; Greenwood et al., 1995). However, individual seroprevalence in this study (8.9%) was lower than that reported in Syria (12.1%), Switzerland (42%), and USA (31%) (Grewal et al., 1986; Krieg and Peterhans, 1990; Giangaspero et al., 1992). On the contrary, this individual goat seroprevalence was significantly higher than that reported in Saudi Arabia (1.9%) (Alluwaimi et al., 1990). A statistical difference was observed in the seroprevalence in respect to the three studied geographical regions. The northern part of Jordan had the highest seroprevalence rate. About 55% of the total population of goats in

K. Al-Qudah et al. / Small Ruminant Research 66 (2006) 181 186 185 Jordan is located in the northern part of the kingdom. In this region, the majority of herds (72%) are of large herd size, which increase the stocking density and eventually increase the likelihood of transmission. This could explain the high seroprevalence rate of CAEV in this region when compared to that of the central or southern parts of Jordan. More detailed epidemiological studies are needed to elucidate other factors, such as climate that could contribute to high CAEV seroprevalence in the northern part of Jordan. In this study, goats older than 3 years of age were more likely to be CAEV seropositive than younger goats. Similar finding were reported previously (Dawson and Wilesmith, 1985; Greenwood et al., 1995). Other studies suggested that CAEV infection occurs in goats older than one year with the same magnitude (Rowe et al., 1991, 1992). Cutlip et al. (1992) indicated that CAEV prevalence increased with age to 3 years. Our data suggest that large herd size, addition of new animals and contact with other goat herds are risk factors for high seropositivity to CAEV. Large herd size and stocking density have been suggested as risk factors previously (Greenwood et al., 1995). In contrast, a Canadian study on a relatively small goat herds suggested an association between CAEV seropositivity and small herd size. Cutlip et al. (1992) suggested that herd size has no impact on seropositivity to CAEV. Addition of new animals and contact with other goat herds has been suggested as important transmission factors for many infectious diseases including CAEV infection (Rowe and East, 1997). Previous studies have reported significant reduction in herd seroprevalence to CAEV in goat herds reared on pasteurized milk (East et al., 1987; Rowe et al., 1991; Peretz et al., 1994). In this study, we were not able to study this factor since pasteurized rearing is not practiced in Jordan. However, rearing system (intensive versus semi-intensive) has no impact on CAEV seropositivity. The incidence of CAEV infection in Jordan has been increased directly by the end of the kidding season. Most of the new cases (58%) were in kids less than 2 months of age. It is possible that those kids became seropositive during their perinatal period. Previous reports have suggested the perinatal period a critical period for CAEV transmission (Robinson and Ellis, 1985; Rowe et al., 1992; East et al., 1993). References Adams, D.S., Klevjer-Anderson, P., Carlson, J.L., McGuire, T.C., Gorham, J.R., 1983. Transmission and control of caprine arthritisencephalitis virus. Am. J. Vet. Res. 44, 1670 1675. Adams, D.S., Oliver, R.E., Ameghino, E., DeMartini, J.C., Verwoerd, D.W., Houwers, D.J., Waghela, S., Gorham, J.R., Hyllseth, B., Dawson, M., Trigo, F.J., McGuire, T.C., 1984. Global survey of serological evidence of caprine arthritis-encephalitis virus infection. Vet. Rec. 115, 493 495. Alluwaimi, A.M., Abu Elzein, E.M., Hassanein, M.M., 1990. Caprine arthritis-encephalitis antibodies in indigenous sheep in Saudi Arabia. Rev. Elev. Med. Vet. Pays. Trop. 43, 444 445. Al-Majali, A.M., 2005. Seroepidemiology of caprine brucellosis in Jordan. Small Ruminant Res. 58, 13 18. Burgu, I., Akca, Y., Alkan, F., Ozkul, A., Karaoglu, T., Cabalar, M., 1994. Antibody prevalence of caprine arthritis-encephalitis virus (CAEV) in goats in Turkey. Dtsch. Tierarztl. Wochenschr. 101, 390 391. Contreras, A., Corrales, J.C., Sanchez, A., Aduriz, J.J., Gonzalez, L., Marco, J., 1998. Caprine arthritis-encephalitis in an indigenous Spanish breed of dairy goats. Vet. Rec. 142, 140 142. Cutlip, R.C., Lehmkuhl, H.D., Sacks, J.M., Weaver, A.L., 1992. Prevalence of antibody to caprine arthritis-encephalitis virus in goats in the United States. J. Am. Vet. Med. Assoc. 200, 802 805. Dawson, M., Wilesmith, J.W., 1985. Serological survey of lentivirus (maedi-visna/caprine arthritis-encephalitis) infection in British goat herds. Vet. Rec. 117, 86 89. East, N.E., Rowe, J.D., Dahlberg, J.E., Theilen, G.H., Pederson, N.C., 1993. Modes of transmission of caprine arthritis-encephalitis virus infection. Small Ruminant Res. 10, 251 262. East, N.E., Rowe, J.D., Madewell, B.R., Floyd, K., 1987. Serological prevalence of caprine arthritis-encephalitis virus in California goat dairies. J. Am. Vet. Med. Assoc. 190, 182 186. Giangaspero, M., Vanopdenbosch, E., Nishikawa, H., 1992. Lentiviral arthritis and encephalitis in goats in north-west Syria. Rev. Elev. Med. Vet. Pays. Trop. 45, pp. 241 241. Greenwood, P.L., North, R.N., Kirkland, P.D., 1995. Prevalence, spread and control of caprine arthritis-encephalitis virus in dairy goat herds in New South Wales. Aust. Vet. J. 72, 341 345. Grewal, A.S., Greenwood, P.L., Burton, R.W., Smith, J.E., Batty, E.M., North, R., 1986. Caprine retrovirus infection in New South Wales: virus isolations, clinical and histopathological findings and prevalence of antibody. Aust. Vet. J. 63, 245 248. Herrmann, L.M., Cheevers, W.P., McGuire, T.C., Adams, D.S., Hutton, M.M., Gavin, W.G., Knowles, D.P., 2003. Competitive-inhibition enzyme-linked immunosorbent assay for detection of serum antibodies to caprine arthritis-encephalitis virus: diagnostic tool for successful eradication. Clin. Diagn. Lab. Immunol. 10, 267 271. Houwers, D.J., van der Molen, E.J., 1987. Initial cases of caprine arthritis-encephalitis virus in the Netherlands. Tijdschr. Diergeneeskd. 112, 1054 1061. Knight, A.P., Jokinen, M.P., 1982. Caprine arthritis-encephalitis. Compend. Cont. Educ. Pract. Vet. 4, S263 S269. Krieg, A., Peterhans, E., 1990. Caprine arthritis-encephalitis in Switzerland: epidemiologic and clinical studies. Schweiz. Arch. Tierheilkd. 132, 345 352. Literak, I., Skrivanek, M., Skalka, B., Celer Jr., V., 1995. Antibodies to certain infections on large goat farms in the Czech republic. Vet. Med. (Praha) 40, 133 136. Martin, S.W., Meek, A.H., Willeberg, P., 1987. Veterinary Epidemiology. Iowa State University Press, Ames, IA. Matthews, J.G., 1999. Diseases of the Goat, second ed. Blackwell Science, Chelmsford, UK, pp. 80 87. Peretz, G., Bugnard, F., Calavas, D., 1994. Study of a prevention program for caprine arthritis-encephalitis. Vet. Res. 25, 322 326.

186 K. Al-Qudah et al. / Small Ruminant Research 66 (2006) 181 186 Pugh, D.G., 2002. Sheep and Goat Medicine. W.B. Saunders Company, Philadelphia, pp. 126, 239 240, 296, 388. Robinson, W.F., Ellis, T.M., 1985. Caprine arthritis-encephalitis virus infection: from recognition to eradication. Aust. Vet. J. 63, 237 241. Rogan, W.J., Gladen, B., 1978. Estimating prevalence from the result of a screening test. Am. J. Epidemiol. 107, 71 76. Rowe, J.D., East, N.E., 1997. Risk factors for transmission and methods for control of caprine arthritis-encephalitis virus infection. Vet. Clin. North Am. Food Anim. Pract. 13, 35 53. Rowe, J.D., East, N.E., Franti, C.E., Thurmond, M.C., Pedersen, N.C., Theilen, G.H., 1992. Risk factors associated with the incidence of seroconversion to caprine arthritis-encephalitis virus in goats on California dairies. Am. J. Vet. Res. 53, 2396 2403. Rowe, J.D., East, N.E., Thurmond, M.C., Franti, C.E., 1991. Risk factors associated with caprine arthritis-ecncephalitis virus infection in goats on California dairies. Am. J. Vet. Res. 52, 510 514. Smith, M.C., Sherman, D.M., 1994. Goat Medicine. Lea & Febiger, Philadelphia, pp.73 79, 135 138. Torres-Acosta, J.F.J., Gutierrez-Ruiz, E.J., Butler, V., Schmidt, A., Evans, J., Babington, K., Bearman, K., Fordham, T., Brownlie, T., Scroer, S., Camara, E., Lightsey, J., 2003. Serological survey of caprine arthritis encephalitis virus in 83 goat herds of Yucatan, Mexico. Small Ruminant Res. 49, 207 211.