José C. Segura-Correa

Seroprevalence of and risk factors for infectious bovine rhinotracheitis in beef cattle herds of Yucatan, Mexico.

The main objective of this cross-sectional study was to estimate the seroprevalence of infectious bovine rhinotracheitis (IBR) in a population of non-vaccinated beef cattle in the livestock region of Yucatan, Mexico and to determine potential risk factors related to the seroprevalence. Also, we estimated the intraherd correlation (r(e)) and design effect (D) of IBR seropositivity. Cattle were selected by two-stage cluster sampling. Blood samples were collected from 564 animals from 35 herds. Sera were tested for antibodies against IBR using the serum-neutralisation test. Information regarding the herd and each animal sampled were recorded through a personal interview with the farmer or farm manager. The data were analysed using fixed-effects logistic multiple regression. Thirty-four of the 35 herds had at least one seropositive animal. The animal true seroprevalence was 54.4%. Animals in large herds or in production had higher odds of seropositivity than those in small herds or growing. The r(e) and D were 0.17 and 3.62, respectively.

Seroprevalence of and Risk Factors for Leptospiral Antibodies among Cattle in the State of Yucatan, Mexico

Sera obtained from cattle in the state of Yucatan, Mexico, were screened using the microscopic agglutination test against 13 serovars of Leptospira interrogans. A total of 62.8% (461/734) cows were positive for one or more serovars. This seroprevalence probably reflects infection because vaccination against leptospirosis has not been practised in Yucatan. The most common antibodies detected were those against antigens of serovars hardjo (54.1%) and tarassovi (53.3%). Region was the only risk factor associated with the seroprevalence of leptospirosis (p < 0.05).

Toxoplasma gondii Presence in Women with Spontaneous Abortion in Yucatan, Mexico

Abstract: The objective of this study was to estimate the seroprevalence of anti–Toxoplasma gondii antibodies and DNA of women with spontaneous abortions in 2 hospitals located in Yucatan, Mexico. Between June 2008 and May 2009, blood samples were taken from 100 women with spontaneous abortion attending the Ticul City Communitarian Hospital and the Merida Mother–Kid Hospital. The sera were tested for anti–T. gondii IgG and IgM antibodies. Blood samples (5 ml with anticlotting agent) were also used for polymerase chain reaction (PCR) assay, to detect T. gondii DNA. Forty-two of the 100 samples were negative. Of the positive samples (n = 58), 32 were positive to IgG, 2 to IgM, 5 to IgG and IgM, 6 to IgG and PCR, 1 to IgM and PCR, and 12 to IgG, IgM, and PCR. Accordingly, 55% of the women were seropositive to at least IgG, 20% to at least IgM, and 19% via PCR. Differences between hospitals were significant (P < 0.05) only for IgM. The risk of infection (IgM positive) was 2.85 (odds ratio [OR] 95%, confidence interval [CI]; 1.03–7.87) times greater in women patients at the Merida Mother–Kid Hospital, than those at the Ticul Communitarian Hospital. More studies are needed to evaluate the impact of this disease and to establish strategies to follow in order to reduce congenital toxoplasmosis in the populations at risk.

Prevalence and Risk Factors of Toxoplasma gondii in Fattening Pigs Farm from Yucatan, Mexico

The objective of this study was to estimate the prevalence and identify risk factors associated with the presence of Toxoplasma gondii in pig-fattening farms from Yucatan, Mexico. A cross-sectional study was conducted with a two-stage sampling. There were 429 pigs sampled from 39 farms randomly selected. Blood samples were collected to obtain DNA and serum. The presence of IgM and IgG antibodies was determined by indirect ELISA. Prevalence was estimated by diagnostic test. Potential risk factors to be included in a marginal logistic regression were tested by chi-square or Fisher. The prevalence of IgM and IgG was 92.5% (397/429) (CI 89.9–95.1%) and 95.8% (411/429) (CI 93.7–97.8%), respectively. Regarding PCR, a prevalence of 50.8% (218/429) (CI 45.9–55.6%) was found. The logistic regression showed an association with herd size and type of feeder (P < 0.05). The risk of a case in farms with ≤400 pigs was 27.9 times higher than in farms with >400 pigs. The manual feeder was a significant protective factor associated with the seropositive against T. gondii. Results indicate a high circulation of T. gondii in pig-fattening farms from Yucatan, finding an increased risk of infection for those farms with less than 400 animals and automatic feeders.

Prevalence and Risk Factors of Toxoplasma gondii Infection in Domestic Cats from the Tropics of Mexico Using Serological and Molecular Tests

The aim of this study was to determine the prevalence and risk factors associated with Toxoplasma gondii infection in domestic cats using an indirect-ELISA (IgM and IgG) and PCR. Samples collected from 220 cats from Merida, Yucatan, Mexico, were analyzed. Cases were reported as acute or chronic. Cases when positive to IgM and IgG and PCR were considered as reactivated chronic infection. Risk factors (sex, age, body condition, diet access to hunting, and number of cats in home) were assessed with a multivariate analysis, 75.5% (166/220) of the cats were IgM and 91.8% (202/220) IgG-seropositive and 79% were PCR-positive (173/220). Number of cats per household and low body condition score were associated with reactivated chronic infection (P < 0.05). It is concluded that T. gondii is scattered in the studied population with several periods of reinfection, and therefore an environmental contamination with infecting oocysts exists and there are intrinsic associated factors in cats that increase the risk of becoming infected.

Risk factors for Aujeszky’s disease in pig herds and detection of field virus antibodies in fattening pigs in the state of Yucatan, Mexico

Two epidemiological studies were conducted from August 1997 to May 1998: a case-control study to identify herd level risk factors for antibodies to Aujeszkys disease virus (ADV) in sows in the state of Yucatan, Mexico and a cross-sectional study to determine the prevalence of antibodies against ADV in fattening pigs. In the case-control study, data on herd management and biosecurity were obtained from all the 27 ADV known field-virus-seropositive farms (cases) and 62 randomly selected seronegative farms (controls) by questionnaire. Breeding animals of these seropositive farms had received a gE-deletion vaccine. In the cross-sectional study, 26 farrow-to-finish farms of the 27 seropositive farms were used and blood samples taken from 60 fattening pigs per herd (15 pigs for each stage of production). Serum samples were analyzed by the screening-ELISA and gE-ELISA tests. In the case-control study, three of the 15 risk factors were significant. Odds ratios for distance to the nearest farm (< or = 2.5km), not sampling for the detection of ADV and herds with origin of breeding animals within the state were 9.5, 18.1 and 8.7. In the cross-sectional study, 11 (42.3%) of the 26 sampled farms were seropositive to vaccine antibodies. None of the piglets were positive to antibodies against field virus risk--suggesting that the strategy of vaccinating only the breeding animals reduced the ADV infection of the piglets.

Prevalence of abortion and stillbirth in a beef cattle system in Southeastern Mexico

Prenatal mortality is an important cause of production losses in the livestock industry. This study estimates the prevalences of abortion and stillbirth in a beef cattle system and determines the significance of some risk factors, in the tropics of Mexico. Data were obtained from a Zebu cattle herd and their crosses with Bos taurus breeds, in Yucatan, Mexico. The logit of the probability of an abortion or stillbirth was modeled using binary logistic regression. The risk factors tested were: year of abortion (or calving), season of abortion (or calving), parity number and dam breed group. The effect of twins on stillbirth was tested using Fisher exact test. Of the 4175 calvings studied 49 were abortions (1.17%). Significant factors in the logistic regression analysis for abortions were season of abortion and parity number. The risk of abortion was lower in the dry seasons compared to the rainy and windy seasons (P = 0.009). The risk of abortion was higher in second parity cows followed by the third and first parity cows, as compared to older cows (P = 0.015). Of the 4126 births, 87 were stillbirths (2.11%). Significant factors in the logistic regression analysis for stillbirth were year of calving (P = 0.0001) and parity number (P < 0.001). The risk of stillbirth in first parity cows was 2.6 times that of old cows. Of the total births, 15 were twins (0.36%) of which 7 were born dead calves. Herd owners must focus on the significant risk factors under their control to reduce the prevalence of prenatal mortality.

Toxoplasma gondii in women with recent abortion from Southern Mexico

Abstract Objective To estimate the presence, parasite burden, percentage of avidity and risk factors to seropositivity for Toxoplasma gondii ( T. gondii ) in women with recent abortion attended at the two main hospitals from Merida, Yucatan, Mexico. Methods Seroprevalence and IgG avidity were estimated from 161 blood samples from aborting women and risk factors associated with serological status were determined. Only 130 from 161 samples were analyzed by quantitative PCR (qPCR) and a nested-PCR (nPCR) to detect T. gondii -DNA. Results Seroprevalence of Toxoplasma IgM and IgG was 3.72% (6/161) and 59.00% (95/161), respectively; 98.94% (94/95) of the women showed high-avidity index and only 1.05% (1/95) demonstrated low-avidity. For qPCR, 3.84% (5/130) of the samples were detected with T. gondii -DNA and all positive samples showed a low parasite load ( P Conclusions In this study, the detection of T. gondii -DNA in IgG-positive women suggests in some cases active parasitemia, even when they demonstrated high-avidity index. Reinfection cases could be presented due to the high circulation of the parasite in the study region. T. gondii could play an important role as cause of abortion and municipal potable-water could be an important risk factor of infection.

Genetic parameters for birth weight, weaning weight and age at first calving in Brown Swiss cattle in Mexico

Heritabilities and genetic correlations between birth weight (n = 13,741), adjusted 240-day weaning weight (WW, n = 8,806) and age at first calving (AFC, n = 3,955) of Brown Swiss cattle in Mexico were estimated. Data from 91 herds located in 19 of 32 states of Mexico from 1982 to 2006 were provided by the Mexican Brown cattle Breeder Association. Components of (co)variance, direct and maternal heritabilities were estimated for birth weight, WW and AFC using bivariate animal models. Direct and maternal heritabilities were 0.21 and 0.05 for birth weight, 0.40 and 0.05 for WW, whereas direct heritability for AFC was 0.08. The correlations between direct and maternal effects for birth weight and WW were −0.49 and −0.64, respectively. The genetic correlations between birth weight–WW and WW–AFC were 0.36 and −0.02, respectively. Under the conditions of this study, selection for increasing birth weight would increase WW, but increasing WW will not change AFC.

Productividad de ovejas F1 Pelibuey x Blackbelly y sus cruces con Dorper y Katahdin en un sistema de producción del trópico húmedo de Tabasco, México

El objetivo de este estudio fue evaluar el comportamiento reproductivo y productividad de ovejas F1 Pelibuey x Blackbelly (P x B) y sus cruces con Dorper y Katahdin (Sintetico). Se analizaron 1.612 datos de intervalos entre partos (IEP), 1.265 de prolificidad (Pr), 1.263 de peso de la camada al destete ajustado a 91 dias (PCDA) y 1.200 de productividad (PROD). El modelo estadistico incluyo los efectos fijos de grupo racial materno (GRM), ano de parto (AP), epoca de parto (EP), numero de parto (NP) y tamano de la camada al destete (TCD), grupo de intervalos entre partos (GIP) y las interacciones de primer orden. El efecto de la madre dentro de GRM fue incluido como efecto aleatorio. Se calculo el indice de constancia de IEP, Pr, PCDA y PROD. Las medias generales de Pr, IEP, PCDA y PROD fueron 1,2 ± 0,01 corderos, 261,5 ± 1,9 dias, 18,5 ± 0,1 kg y 16,8 ± 0,2 kg de cordero destetado, respectivamente. Excepto por grupo racial materno, todos los factores considerados en este estudio afectaron a todas las variables de respuesta. Asimismo la epoca de parto no afecto la prolificidad. Los indices de constancia estimados fueron 0,05 ± 0,03, 0,13 ± 0,03, 0,10 ± 0,03 y 0,12 ± 0,03 para IEP, Pr, PCDA y PROD, respectivamente. Las correlaciones parciales de PROD con IEP y PCDA fueron -0,56 y 0,84, respectivamente. Se concluye que la productividad del grupo racial materno P x B es similar al grupo Sintetico, y que los efectos ambientales tienen mas importancia que los efectos geneticos.