J. Vet. Med. B 39, 290-298 (1992) 0 1992 Paul Parey Scientific Publishers, Berlin and Hamburg ISSN 093 1 - 1793 Enfermedades Infecciosas, Departamento de Patologia Animal, Facultad de Veterinaria, Universidad de Murcia, Espaiia Sero-Epidemiological Survey of Porcine Respiratory Coronavirus (PRCV) Infection in Breeding Herds in Southeastern Spain M. J. CUBERO, L. LEON, A. CONTRERAS, I. LANZA, E.ZAMORA and M. R. CARO Address of authors: Dr. M. J. CUBERO, Enfermedades Infecciosas, Departamento de Patologia Animal, Facultad de Veterinaria, Complejo Universitario de Espinardo, 30071 Murcia, Espafia 34% of the infected herds showed a medium prevalence (30-59%) and in only 10% of the infected farms was the prevalence low (6-29 %) (Table 2). Factors associated with PRCV-infection Geographical zone. There was a significant association (p 0.01) between geographi- cal zone and the number of PRCV-infected breeding herds. The Cartagena zone Table 4. Farms and breeding pigs censused, analysed and infected by PRCV in the four herd sizes of the Murcia Region Herd sizeab Family Small Medium Large Total Farms Censused Analysed Infected (no) Infected (YO) c. I,;:.: Breeding pigs Censused Analysed Positive (no) Positive (7) c, I,:. 1,957 120 14 11.66 5.74 10,343 600 32 5.33 1.79 3,576 120 19 15.83 6.53 75,770 1,200 79 6.58 1.40 464 120 33 27.50 7.98 30,612 1,800 273 15.16 1.65 284 120 39 32.50 8.38 72,049 2,400 488 20.33 1.61 6,281 480 105 21.87 7.38 188,774 6,000 872 14.53 0.89 :c Family (1 -9 breeding pigs); small (10-49); medium (50-99) and large (2 100). w C. I. confidence interval for security coefficient of 95 %. Sero-Epidemiological Survey of Porcine Respiratory Coronavirus 295 (39.16 f 8.73 Yo) showed a more increased risk (p 0.01) of infection than the Guadalentin Valley (18.33 rf: 6.92 YO), the Huerta of Murcia (12.50 f 5.91 %) and the Rest of Region (17.50 ? c 6.79 %) (Table 3). Herd size. The association between the number of PRCV-infected breeding herds and herd size was also significant (p 1 0 0 category, 32.50 f 8.38 %) than those in which there were 100 breeding pigs. This sample size was statistically significant (95 % confidence interval) for the prevalence of infection detected. Of the random serum samples, 15.61 % were found PRCV- and/or TGEV-positive by indirect ELISA using the international reference strain Purdue (37, 38), and subse- quently 14.53 % were found PRCV-positive when monoclonal blocking ELISA was applied. The prevalence of PRCV-infection in breeding pigs (14.53 * 0.89 %) in the Murcia Region is similar to that reported by BEREITER et al. (5) in Switzerland (13 Y O ) but lower than that of other surveys: 30.5 % in North-East Spain (36), 55 % in Austria (8), 68 / o in Belgium (I), 73.70 % in France (4) and 87 % in Central Spain (9). The low prevalence of PRCV-infection in the breeding pigs (14.53 +. 0.89 %) and breeding herds (21.87 * 7.38 %) of the Murcia Region may be explained by the recent appearance and spread of PRCV in the breeding herds of South-East Spain in 1987. In the European swine population, after the spread of PRCV-infection, a lower or absent prevalence of TGEV-infections has been found in serological surveys. The preva- lence of TGEV-infection, both on breeding farms (5.00 f 1.94 %) and in breeding pigs (1.26 f 0.28 %) in the Murcia Region (39) is similar to that (6 % infected farms and 1 YO seropositive pigs) reported by BEREITER et al. (5) in Switzerland, but lower than that found in surveys conducted in other countries (1,28,29,31,32) before the appearance of PRCV- infection. When the blocking ELISA technique was applied in countries such as Austria, where surveys recorded high levels of seroreaction to TGEV, the positive reactions were observed to be due entirely to PRCV (8). The present association in European countries between a high prevalence of PRCV and a low incidence of TGEV cannot in itself be taken as conclusive evidence of cross-pro- tection, since TGE incidence has been known to fluctuate widely in the past (40). No evi- dence for cross-protection between immunity to PRCV and TGEV was found (40,41,42). In countries where the PRCV has been isolated, the infection presents a wide geographical spread (43). PRCV is enzootic in the swine populations of Belgium (44), Great Britain (2), Netherlands (7) and Denmark (10). Likewise, PRCV-infection appears spread throughout the four geographical zones of the Murcia Region. However, we found 296 CUBERO, LEON, CONTRERAS, LANZA, ZAMORA and CARO a correlation (P 0.01) between the geographical zone and number of PRCV-infected farms. The farms in the Cartagena zone have a greater risk of infection. HENNINGSEN et al. (45) found a pronounced positive association between the size of the herd as measured by the number of heat producing units (HPU) and the risk for porcine coronavirus seroconversion. Likewise, in our survey the size of the farm and the rate of contagiousness in the animals hous