The Effect of Parasitic Worm Infections on the Immune Response to Tuberculosis Bacteria
Condition: Intestinal Helminth Infection; Filarial Infection
MeSH terms: Infections; Communicable Diseases; Helminthiasis
Study type: Observational

Summary: 
      This study, sponsored by the National Institutes of Health and the Tuberculosis Research
      Centre in Chennai, India, will examine how helminth and filarial infections affect the immune
      response to mycobacteria (the bacteria that causes tuberculosis). Helminths are parasitic
      worms that infect the gut, and filaria are worms that circulate in the blood and infect
      various tissues. The findings of this study may affect how tuberculosis is assessed in
      Chennai, where filarial and helminth infections are common in the population.

      Patients between 6 and 65 years of age with helminth or filarial infections who do not have
      active tuberculosis, cancer, AIDS, or other immunosuppressive illness may be eligible for
      this study. Participants will be recruited from villages in the Chingleput District of
      Chennai, India.

      Participants will complete a medical history and physical examination. They will have a blood
      test to determine red blood cell count and to detect filarial infection, a stool examination
      to detect helminth infection, and a tuberculin skin test for tuberculosis. Patients with a
      positive tuberculin test will be treated for tuberculosis and any filarial or helminth
      infections that may have been detected.

      Patients whose tuberculin test is negative will be invited to participate in the second part
      of the study-to determine whether people with either filarial infections or helminth
      infections, or both, respond to tuberculosis bacteria in the same way as people who do not
      have these infections. Participants will undergo a review of their medical history, a
      physical examination, and a blood test to assess red blood cell levels and to look for
      evidence of filarial or helminth infection. They will then be randomly assigned to receive
      either albendazole and DEC (anti-helminth and anti-filarial drugs) or a placebo (look-alike
      tablets that do not contain an active ingredient). Two months later, patients will receive a
      second dose of the same tablets (placebo or active drug) they took previously, and after
      another 4 weeks they will be re-tested for tuberculosis. After 6 months (at the end of the
      study) all participants will receive anti-helminth and anti-filarial drugs and will have a
      repeat tuberculin skin test. Blood and stool samples will be collected twice in the 6-month
      period after the initial treatment to determine the levels of antibody against the parasites,
      to measure the level of infection with filaria, and to measure the level of red blood cells.
    

Detailed description: 
      To determine if preexisting intestinal helminth infection or filarial infection alters the
      immune response to mycobacterial antigens or the clinical expression of tuberculosis, this
      study proposes to assess the skin test reactivity to tuberculin (PPD) in a community in which
      intestinal helminth infection, filarial infection and tuberculosis co-exist. Once baseline
      data are obtained, all those who are PPD negative (but who harbor helminth parasites) will be
      randomized to receive either anthelminthics or placebo twice over a six week period. One and
      4 months following the last dose, change in PPD status will be assessed as will the
      intestinal and filarial parasite burden. By assessing these changes, the influence of
      intestinal helminth or filarial infection on the cellular immune response to Mycobacterium
      tuberculosis can be determined.
    

Keywords: Filarial Infections; Helminths; Tuberculosis; Filarial Infection