Determinants of Primary Amoebic Meningoencephalitis infection in Karachi, Pakistan-2019

  • Water or foodborne
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Primary amebic meningoencephalitis (PAM) is an acute, fulminant, and fatal central nervous system infection caused by an amoeba, Naegleria fowleri. It occurs naturally in warm, freshwater bodies. Infection occurs only when contaminated water enters the nasal passages. Since 2014 PAM has been recognized as a continuing problem in Karachi. We did a case-control study to identify risk factors for PAM in Karachi.

We defined cases as PCR confirmed cases of PAM infection among the residents of Karachi, during 2017-2019. Hospital records were reviewed. Using a standard questionnaire, we interviewed family members about nasal irrigation and other nasal exposures to the water in 29 PAM cases. For each case, three age-sex matched controls were recruited from the same neighborhoods and interviewed with the same questionnaire. We measured the chlorination levels of the household water of cases. We computed frequencies, attack rates (AR), and using conditional logistic regression, adjusted odds ratios (aOR) and 95% confidence intervals (CI).

During 2017-2019, 29 PAM cases (AR 3/100,000 population) from 5-55 years old (median: 30) with a male to female ratio of XX were reported. Cases experienced fever (100%), coma (100%), neck stiffness (97%) and headache (52%). All died from 3–7 days after onset. Cases peaked in June (n=7; 25%) and July (n=8; 29%) when the mean ambient air temperatures reached 31.6C. Of cases, 76% had performed nasal irrigation during ablution compared to 24% of controls (aOR 15, 95% CI 5.1-41). Residual chlorine levels in the household water were found to be below 0.2 mg/l.

Performing nasal irrigation with inadequately chlorinated water during ablution was the most probable cause of PAM in Karachi. Using boiled or chlorinated water for nasal irrigation during ablution was recommended. A community awareness campaign was including infographics displayed in the mosques and health awareness to the general public.

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