# Detection of Haemophilus ducreyi from environmental and animal samples in Cameroon

## TL;DR

The study found that Haemophilus ducreyi, a bacteria causing skin ulcers, was detected on clothing and in flies in Cameroon, suggesting they might help spread the infection.

## Contribution

This study is the first to detect Haemophilus ducreyi in flies and on clothing, suggesting potential mechanical and passive transmission routes.

## Key findings

- Haemophilus ducreyi was detected on clothing (13.3%) and in flies (27%).
- Flies also tested positive for Treponema pallidum subspecies pertenue at a lower rate (2.6%).
- No Haemophilus ducreyi was found in environmental samples like water or fomites.

## Abstract

Children in parts of Africa, the South Pacific, and Southeast Asia frequently develop cutaneous ulcers caused by two bacteria: Haemophilus ducreyi (HD) and Treponema pallidum subspecies pertenue (causative agent of yaws). The World Health Organization (WHO) aims to eradicate yaws using mass administration of azithromycin. This also leads to a temporary decrease in ulcers caused by HD followed by a rebound suggesting an ongoing reservoir of infection. The aim of this study was to investigate whether HD could spread through the environment or animals.

Alongside detection of human cases of cutaneous ulcers from villages in Cameroon, we additionally collected samples from animals (dogs, cats, flies), fomites (bedsheets, clothing, benches, doors), and water sources (marigots and lakes). DNA was extracted and tested for HD and T. pallidum using two specific qPCR assays.

HD was not detected in any of the environmental samples but it was on both clothing (13.3%) and in flies (27%). Flies also tested positive for T. pallidum, but at a lower rate (2.6%).

These results suggest that flies and some fomites may contribute to the transmission of HD. Future research should focus on determining whether either of these are capable of carrying live bacteria that can cause onward transmission.

Cutaneous ulcers are a significant public health concern, particularly among children in tropical regions of the Pacific, Southeast Asia, West and Central Africa. These lesions are primarily caused by HD, the etiological agent of chancroid, and Treponema pallidum subspecies pertenue, responsible for yaws. To eliminate these infections by 2030, WHO advocates mass drug administration (MDA) with azithromycin, a more effective and less invasive alternative to benzathine penicillin. However, HD infections persist in endemic areas despite these efforts. In this study, we explored the potential role of environmental and animal reservoirs in sustaining HD transmission. Our findings confirm the presence of HD in flies and on clothing, suggesting that these may act as mechanical and passive vectors, respectively, contributing to the persistence of ulcers even after antibiotic treatment. These results underscore the need for complementary strategies, including improved hygiene measures, to effectively achieve eradication.