Mycobacterium ulcerans in mosquitoes captured during outbreak of Buruli ulcer, southeastern Australia

Abstract

Buruli ulcer (BU) occurs in >30 countries. The causative organism, Mycobacterium ulcerans, is acquired from the environment, but the exact mode of transmission is unknown. We investigated an outbreak of BU in a small coastal town in southeastern Australia and screened by PCR mosquitoes caught there. All cases of BU were confirmed by culture or PCR. Mosquitoes were trapped in multiple locations during a 26-month period. BU developed in 48 residents of Point Lonsdale/Queenscliff and 31 visitors from January 2001 through April 2007. We tested 11,504 mosquitoes trapped at Point Lonsdale (predominantly Aedes camptorhynchus). Forty-eight pools (5 species) were positive for insertion sequence IS2404 (maximum likelihood estimate 4.3/1,000), and we confirmed the presence of M. ulcerans in a subset of pools by detection of 3 additional PCR targets.

Figure 1

Ear of an 18-month-old child with culture- and PCR-confirmed Buruli ulcer who briefly visited St. Leonards, Australia, in 2001 (Figure 2). The initial lesion resembled a mosquito bite or that of another insect.

Figure 2

Map of central coastal Victoria, Australia, showing towns and places referred to in the text or in associated references.

Figure 3

Map of Point Lonsdale/Queenscliff, Australia (postcode 3225), showing location of houses of affected permanent residents, mosquito traps, and other features mentioned in the text. Not all traps yielded PCR-positive mosquitoes during the trapping period. Neg, negative; pos, positive.

Figure 4

Epidemic curve of cases of Buruli ulcer linked to Point Lonsdale/Queenscliff, Australia, by resident/visitor status and month of reporting, 2002–2007.

Figure 5

Cases of Buruli ulcer epidemiologically linked to Point Lonsdale, Australia, by resident/visitor status, age, and sex. Dashed lines are medians.

Figure 6

Estimated age-specific attack rates of Buruli ulcer for residents of Point Lonsdale/Queenscliff, Australia (postcode 3225). Values above the bars are cases per total no. residents in each age group.