Analysis of Bovine Tuberculosis Transmission in Jalisco, Mexico through Whole-genome Sequencing

Bovine tuberculosis, caused by M. bovis, is endemic in Mexico and has had a big impact on public health. Jalisco is considered to be an important dairy region in the country, accounting for approximately 19% of the total milk production. Within Jalisco, the region of Altos Sur holds the largest proportion of the cattle inventory of the state.

To determine the frequency of bovine tuberculosis in Altos Sur, Jalisco, as well as M. bovis genetic diversity, sampling of tissue (lymph nodes, lungs, and liver) from Holstein cattle was performed in four abattoirs belonging to three municipalities of this region (Tepatitlán de Morelos, San Miguel el Alto, and Arandas). Spoligotyping and whole-genome sequencing were carried out to assess the genetic relationships of M. bovis strains circulating in this area, as well as a comparison to isolates from other places in Mexico.

Prevalence was 15.06%, and distribution similar among the three municipalities. The most frequent spoligotypes were SB0673, SB121, and SB0145. Whole-genome sequencing revealed three main clades (I, II, III), but isolates did not show clustering by region.

Phylogenetic analysis suggested ongoing transmission between herds of the different regions, and no unique source of infection was determined. This hinders efforts under the national program for the control and eradication of the disease, so serious attention must be paid to rural regions such as Altos Sur in order to improve its success.