Spatial distribution models of seroreactive sheep to Leptospira spp. in Veracruz, Mexico.

Leptospirosis is an infectious zoonotic disease of special importance in tropical regions of the world and is closely related to climatic conditions. In Mexico, at least eight Leptospira serogroups are known to affect sheep, but little is known about their distribution. The aim was to analyse the spatial distribution of seroreactive sheep to eight serogroups of Leptospira spp. through ecological niche modelling from the state of Veracruz. We carried out a cross-sectional, multistage, and stratified epidemiological study, sampling 405 sheep in different regions of the state (north, center, and south). The sera were analysed using the microscopic agglutination test (MAT) to identify seropositivity to eight Leptospira serogroups (Icterohaemorrhagiae, Pyrogenes, Grippotyphosa, Canicola, Pomona, Hardjo, Wolffi, and Tarassovi). Management variables in the sampled herds were evaluated through a survey among the producers, which was analysed using the chi-squared test for cross-tabulation. Geospatial modelling was conducted using MAXENT and 19 climatic variables, and validation was carried out using the area under the curve (AUC). No positive animals were found for Pomona in any area of Veracruz, and there was only one case of seroreactivity to Grippotyphosa. The total seroprevalence found was 53.83% (95% confidence interval [CI] 48.84-58.75). The main serogroup found was Sejroe (55.31%, 95% CI 50.32-60.20%), followed by Canicola (8.64%, 95% CI 6.17-11.92%), Icterohaemorrhagiae (4.69%, 95% CI 2.93-7.36%), Tarassovi (3.95%, 95% CI 2.35-6.47%), Pyrogenes (2.47%, 95% CI 1.26-4.64%), Australis (0.99%, 95% CI 0.32-2.69%), and Grippotyphosa (0.25%, 95% CI 0.01-1.59%). The predictive model for Australis was not significant. Acceptable predictive models (AUC > 0.7-0.8) were found for Canicola, Icterohaemorrhagiae, Pyrogenes, and Tarassovi, while for Sejroe, it was excellent (AUC > 0.85); consequently, the climatic variables that most contributed to the model were those related to precipitation. The potential distribution of Pyrogenes, Icterohaemorrhagiae, and Canicola was located to a greater extent in the three regions; Pyrogenes and Tarassovi were distributed mostly in the north and central regions, and Sejroe was mostly located in the center and south of the state. Ecological niche modelling could support epidemiological control and surveillance programs for affected sheep herds in the state of Veracruz.

[Diagnostic serology of swine leptospirosis in Mexico 1995-2000]. / Serología diagnóstica de leptospirosis porcina en México 1995-2000

Results obtained from sample testing of 1970 swines from a number of Mexican farms were analyzed. Such samples had been received in the Leptospira Lab of Universidad Autonoma Metropolitana de Xochimilco from 1995 to 2000. Sera with titers equal to or higher than 1:1000 were considered positive; 39,8% of the animals were seropositive (784) and the most frequent serovarieties were bratislava, 22.5%; icterohaemorrhagiae strain Palo Alto, 14,5%; portland vere strain Sinaloa ACR, 13,8%; icterohaemorrhagiae, 11,1%; grippotyphosa, 8,9%; hardjo strain H89,7.2%; tarassovi,7.1%; panama, 5.8%, pomona and hardjo, 5.1%; wolffi, 3%; shermani, 2.4%; pyrogenes, 1.2%; canicola, 0.8%; hebdomadis, 0,5%. The bratislava serovariety has been reported as the cause of reproductive failure in several countries and it holds the first place in serological studies. Therefore, the present paper provides information for stating that this is one of the most significant serovarieties in Mexico.

[Serological study of bovine leptospirosis in Mexico]. / Estudio serológico de leptospirosis bovina en México.

The results of 4 043 bovine sera samples from various Mexican regions, which were sent to a diagnosis lab, were analyzed. The method was the agglutination technique, taking the dilution rate 1:1000 or higher as positive. The analysis revealed 31,1% of seroprevalence and the most frequent serovarietes were hardjo (strain H 89 isolated in Mexico), wolffi and tarassovi. There is coincidence with early data obtained in Mexico on a 34% of prevalence found in a similar study performed in 1994, and with the scientific literature from other countries. The former study also indicated that tarassovi and wolffi were the most common leptospira, so there is coincidence with the figures in the reviewed literature. It was concluded that there was no significant variation in the prevalence rate between the 1994 study and the present one; therefore, it is recommended that this study be promoted so as to increase the bovine vaccination and achieve a reduction in leptospirosis in Mexico.