Tuberculosis Outbreak on an American Indian Reservation --- Montana, 2000--2001

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During May 2000--January 2001, five tuberculosis (TB) cases, linked by contact and DNA fingerprinting (1), were reported from the Fort Belknap Indian Reservation in rural Montana. Before this, only one case of TB had been reported from the reservation since 1992. To determine the cause of the outbreak, the Fort Belknap Tribal Health Department and the Indian Health Service (IHS) conducted an investigation and requested assistance from the Montana State Department of Public Health and Human Services (DPHHS) and CDC to improve case finding and medical management of persons with TB. This report summarizes the results of the investigation and demonstrates how, in low incidence areas, rapid expansion of local capacity for TB control is critical to eliminate TB in the United States.

Median age of the five TB patients was 44 years (range: 32--61 years); four were male. Isolates from all five TB patients were confirmed as Mycobacterium tuberculosis and were susceptible to first-line drugs (isoniazid, rifampin, pyrazinamide, and ethambutol). At the time of presentation, the index patient had a productive cough and a sputum smear that demonstrated acid-fast bacilli (AFB), suggesting infection with TB. Patient 5 also had sputum smears demonstrating AFB. All five patients were started on directly observed therapy (DOT) for TB.

A contact investigation of the sputum AFB smear-positive index patient yielded 126 contacts, of whom 121 (96%) received a tuberculin skin test; 22 (18%) had positive results. Chest radiographs of the 22 skin test-positive contacts were performed, and clinical and radiographic findings were reviewed for evidence of TB disease. From this investigation, patient 2 was diagnosed with TB disease and was started on treatment with isoniazid and rifampin. Of the 21 persons with latent TB infection (LTBI), 19 were started on treatment with isoniazid, and two persons refused treatment on the basis of previously positive skin tests.

The index patient had a large extended family network and regularly engaged in heavy alcohol consumption with other drinkers in confined spaces. The four secondary patients were all regular drinking partners of the index patient; however, only patient 2 had TB diagnosed by routine contact investigation. The other three were diagnosed when they presented with symptoms of TB. Patient 3, who was also a family member and a drinking partner, was included in the contact investigation but did not have a tuberculin skin test performed because the patient had a previously positive result and a normal chest radiograph. The remaining two secondary patients were not included as contacts because clinical staff focused initially on identifying transmission to extended family members.

To assist with clinical management of patients with TB and with the contact investigation, the reservation health staff sought assistance from the Montana DPHHS TB program and CDC. DPHHS and CDC reviewed the clinical management of the five TB patients and revised treatment regimens to meet current treatment guidelines. Because two of the four secondary TB patients were not named as contacts and subsequently presented to the health facility with TB, a review of the contact investigation was conducted based on skin positivity and TB disease rates. This revealed that regular alcohol-drinking partners of the index patient had a higher risk for infection with M. tuberculosis than nondrinking family members and other social contacts. Of the 26 drinking partners identified, 14 (56%) were infected; of the 42 nondrinking family members identified, seven (18%) were infected; and of the 56 other social contacts, one (3%) was infected.

Collaboration among the Tribal Council, IHS, the Montana DPHHS TB Program, and CDC led to four capacity-building efforts to improve TB clinical management and control on the reservation. First, six staff members from the reservation clinic attended a 1-week course in TB clinical management at the National Jewish Medical and Research Center in Denver, Colorado. The Montana State TB Program provided ongoing consultation to both clinical and public health nursing staff, including weekly case management meetings and assistance with development of DOT and incentive programs. Clinical staff also received advice and educational materials from the Montana State TB Program and the Francis J. Curry National TB Center in San Francisco, a Model Tuberculosis Center funded by CDC. Second, IHS hired an additional tribal health nurse with extensive knowledge of the community to manage the contact investigation and to emphasize case management and adherence to therapy. Third, CDC investigation team members reviewed clinical management practices and made recommendations for improvements. Finally, the team trained staff members in social network analysis to improve future contact investigations.

As of February 2002, four of the TB patients had completed treatment. One elderly patient with end-stage liver disease died from non-TB-related causes 2 months after starting therapy for TB. Of the 19 contacts, 13 (68%) patients had completed their treatment for LTBI, three (16%) had discontinued treatment before completion, and three (16%) had their treatment discontinued by their health-care providers for medical reasons. Of the 19 treated for LTBI, two received treatment by DOT, and the remainder were followed on a weekly basis by public health nursing staff; 18 of the contacts treated for LTBI were provided incentives to improve treatment adherence.

Reported by: J McConnell, K Horn, R Lamere , C Lamere, C Ironmaker, Tribal Health Dept, Fort Belknap Reservation; D Bell, K Nicholson, M Mount, Indian Health Svc, Fort Belknap; R Harding, Indian Health Svc, Billings Area Office; D Ingman, T Damrow, Montana State Dept of Public Health and Human Svc. J Cheek, J Bertolli, Epidemiology Program, Indian Health Svc, Albuquerque, New Mexico. A Gershon, Div of Respirology, Univ of Toronto, Ontario. R Ridzon, J Jereb, Div of Tuberculosis Elimination, National Center for HIV, STD, and TB Prevention; L Thorpe, J Larson, EIS officers, CDC.

Editorial Note:

The findings in this report illustrate that local staff proficiency in the identification and management of persons with TB is necessary in geographic areas with low and declining TB trends, and that resources exist for local health-care providers and TB control programs to expand their outbreak response capacity rapidly. To help maintain and bolster capacity for TB control in low-incidence areas, timely assistance from external sources is an important component of the strategy to eliminate TB in the United States. On this American Indian reservation, recent transmission of M. tuberculosis was confirmed, and initial problems with the contact investigation prompted local health-care providers to mobilize and obtain the requisite information and skills to conduct a thorough investigation. The external support included short-term training courses on TB case management, clinical consultations using national hotlines, educational materials, and assistance from a CDC outbreak response investigation team. On other occasions, CDC also has provided short-term funds for temporary staffing to conduct the additional activities required to respond to an outbreak.

This investigation also confirmed that contact investigations and early review of findings are critical to the control of a TB outbreak. In this instance, the hiring of a tribal nurse with extensive community knowledge expedited the investigation and facilitated a high follow-up rate among contacts and a high completion rate among persons treated for LTBI. However, an earlier systematic review of the relationships between contacts and cases, including social and family contacts, would have led to faster identification of persons at highest risk for infection and disease and might have led to the prevention of secondary TB cases, particularly because previous investigations have determined that heavy alcohol consumption in confined spaces has been associated with M. tuberculosis transmission (2).

The reported case rate of TB in the United States has declined steadily since 1992, reaching a record low of 5.8 cases per 100,000 population in 2000 (3). Case rates among American Indians are approximately twice the national average, but they also have declined at a similar pace during the past decade. TB case rates can start to rise when the public health infrastructure and resources for TB control are reduced or neglected (4). Local expertise in TB management varies widely across the United States. In areas where TB incidence rates are high, resources for TB control might be adequate. In low-incidence areas, TB expertise and resources are often limited. Detailed local and state outbreak response plans should include ways to augment TB control capacity before unexpected increases in M. tuberculosis transmission occur.

References

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