Prevalence of antibodies against Histophilus somni and risk factors in beef cattle in Yucatan, México

Abstract

THE PURPOSE OF THIS STUDY WAS TO ESTIMATE THE SEROPREVALENCE OF H. SOMNI INFECTION AND TO DETERMINE SOME RISK FACTORS ASSOCIATED WITH THE SEROPOSITIVITY IN BEEF CATTLE IN THE LIVESTOCK REGION OF YUCATAN, MEXICO. FURTHERMORE, THE INTRAHERD CORRELATION COEFFICIENT (RE) AND THE DESIGN EFFECT (D) WERE ESTIMATED. THE ANIMALS WERE SELECTED USING A TWO-STAGE RANDOM SAMPLING. BLOOD SAMPLES WERE COLLECTED FROM 490 ANIMALS FROM 35 HERDS, AND SERA WERE TESTED FOR THE DETECTION OF ANTIBODIES AGAINST H. SOMNI, USING THE DOUBLE AGAR GEL IMMUNODIFFUSION TEST. INFORMATION ABOUT EACH HERD AND ANIMAL SAMPLED WAS RECORDED BY A QUESTIONNAIRE PERSONALLY APPLIED IN THE FARM. DATA WERE ANALYZED BY CHI-SQUARE TESTS. TEN HERDS HAD ZERO SEROPOSITIVE ANIMALS, 19 HAD ONE AND SIX HAD TWO SEROPOSITIVE ANIMALS. THIRTY ONE OUT OF 490 ANIMALS WERE SEROPOSITIVE. THE ANIMAL SEROPREVALENCE ADJUSTED TO HERD SIZE WAS 5.5% (95% CONFIDENCE INTERVAL = 3.5%, 7.5%). ANIMAL SEROPREVALENCE IN THE SIX MUNICIPALITIES RANGED FROM 3.6% TO 9.5%, BUT NO SIGNIFICANT DIFFERENCES (P = 0.89) WERE FOUND. THE RE AND D VALUES FOR H. SOMNI SEROPREVALENCE WERE 0 (SE = 0.01) AND 1 (SE = 0.19), RESPECTIVELY. THE CHI-SQUARE TEST DID NOT SHOW ASSOCIATION (P > 0.10) BETWEEN THE PRESENCE OF ANTIBODIES AGAINST H. SOMNI AND THE RISK FACTORS INVESTIGATED.