RESUMO
The Mycobacterium tuberculosis complex (MTBC) species includes both M. tuberculosis, the primary cause of human tuberculosis (TB), and M. bovis, the primary cause of bovine tuberculosis (bTB), as well as other closely related Mycobacterium species. Zoonotic transmission of M. bovis from cattle to humans was recognized more than a century ago, but transmission of MTBC species from humans to cattle is less often recognized. Within the last decade, multiple published reports from around the world describe human-to-cattle transmission of MTBC. Three probable cases of human-to-cattle MTBC transmission have occurred in the United States since 2013. In the first case, detection of active TB disease (M. bovis) in a dairy employee in North Dakota prompted testing and ultimate detection of bTB infection in the dairy herd. Whole genome sequencing (WGS) demonstrated a match between the bTB strain in the employee and an infected cow. North Dakota animal and public health officials concluded that the employee's infection was the most likely source of disease introduction in the dairy. The second case involved a Wisconsin dairy herd with an employee diagnosed with TB disease in 2015. Subsequently, the herd was tested twice with no disease detected. Three years later, a cow originating from this herd was detected with bTB at slaughter. The strain in the slaughter case matched that of the past employee based on WGS. The third case was a 4-month-old heifer calf born in New Mexico and transported to Texas. The calf was TB tested per Texas entry requirements and found to have M. tuberculosis. Humans are the suspected source of M. tuberculosis in cattle; however, public health authorities were not able to identify an infected human associated with the cattle operation. These three cases provide strong evidence of human-to-cattle transmission of MTBC organisms and highlight human infection as a potential source of introduction of MTBC into dairy herds in the United States. To better understand and address the issue, a multisectoral One Health approach is needed, where industry, public health, and animal health work together to better understand the epidemiology and identify preventive measures to protect human and animal health.
RESUMO
OBJECTIVES: Public health laboratories (PHLs) provide essential services in the diagnosis and surveillance of diseases of public health concern, such as tuberculosis. Maintaining access to high-quality laboratory testing is critical to continued disease detection and decline of tuberculosis cases in the United States. We investigated the practical experience of sharing tuberculosis testing services between PHLs through the Shared Services Project. METHODS: The Shared Services Project was a 9-month-long project funded through the Association of Public Health Laboratories and the Centers for Disease Control and Prevention during 2012-2013 as a one-time funding opportunity to consortiums of PHLs that proposed collaborative approaches to sharing tuberculosis laboratory services. Submitting PHLs maintained testing while simultaneously sending specimens to reference laboratories to compare turnaround times. RESULTS: During the 9-month project period, 107 Mycobacterium tuberculosis complex submissions for growth-based drug susceptibility testing and molecular detection of drug resistance testing occurred among the 3 consortiums. The median transit time for all submissions was 1.0 day. Overall, median drug susceptibility testing turnaround time (date of receipt in submitting laboratory to result) for parallel testing performed in house by submitting laboratories was 31.0 days; it was 43.0 days for reference laboratories. The median turnaround time for molecular detection of drug resistance results was 1.0 day (mean = 2.8; range, 0-14) from specimen receipt at the reference laboratories. CONCLUSIONS: The shared services model holds promise for specialized tuberculosis testing. Sharing of services requires a balance among quality, timeliness, efficiency, communication, and fiscal costs.