# Brucella abortus and public health risk: Prevalence in milk sold at open markets in Cameroon

## TL;DR

This study finds Brucella abortus in milk sold at open markets in Cameroon, showing a public health risk due to unsafe milk handling practices.

## Contribution

The study is the first to detect Brucella abortus in milk for human consumption in Cameroon, revealing a new public health risk pathway.

## Key findings

- Brucella abortus was detected in milk samples from open markets in Cameroon using culture, PCR, and sequencing.
- Milk merchants commonly engaged in risky practices like not boiling milk, increasing contamination risks.
- Approximately 720 people per week may be exposed to contaminated milk in these markets.

## Abstract

Brucellosis, a neglected zoonotic disease, is endemic in many sub-Saharan African countries, including Cameroon. Recent studies have shown that Brucella abortus infects multiple livestock species throughout Cameroon. While the presence and risk to humans have been identified at farms and abattoirs, the bacterium has never been detected in milk intended for human consumption. In Cameroon, milk is commonly sold at open-air markets for human consumption without regulation. This study investigates the presence of Brucella spp. in milk sold at these markets in three regions: the Far North, North, and West. Cow milk samples and surveys were collected from 380 merchants in each region, totaling 1,140 samples and surveys. Each sample underwent iELISA, culture, real-time PCR, and next-generation sequencing (NGS). Surveys assessed the knowledge, attitudes, and practices (KAP) of milk merchants. Results indicate that B. abortus is not only endemic in livestock but present in milk sold for human consumption. Culture results show a countrywide positivity of 1.3% (1.1% Far North, 1.1% North, 1.8% West). Real-time PCR results indicate a 4.0% positivity rate (2.4% Far North, 5.5% North, 4.0% West). iELISA indicates 21% of the milk samples contained anti-Brucella antibodies, with significant regional variations (38.4% Far North, 15.5% North, 8.9% West). Finally, NGS revealed that the bacterial isolates from milk are epidemiologically linked to those obtained from animals across the region. KAP analysis shows that only 26.4% of merchants boil and 91.2% mix the milk from multiple cattle before sale. All surveyed merchants selling culture-positive milk engaged in risky behaviors, resulting in the sale of contaminated milk to approximately 720 people each week. This study highlights the risk of human brucellosis extending beyond farms and abattoirs to the general public. Future research should investigate milk consumers’ habits and prevalence to better understand brucellosis risk in Cameroon.

Brucellosis is a neglected disease that affects both animals and humans, particularly in sub-Saharan Africa. In Cameroon, Brucella abortus, a bacterium that primarily infects cattle, has been found to infect multiple livestock species, posing a risk to people working on farms and in slaughterhouses. However, this study reveals that the bacterium is also present in milk sold at open-air markets, which are a common source of food for the general public. Milk samples from 380 merchants in each of three regions were collected and assessed using serology, culture, real-time PCR, and next-generation sequencing of the isolate DNA. It was discovered that B. abortus is indeed present in milk intended for human consumption, and milk merchants engage in well-known risky practices, such as not boiling milk before sale. This finding is significant because it shows that the risk of brucellosis extends beyond livestock handlers to the public that drinks milk. The study highlights the need for better regulation and practices to ensure milk safety, which could help prevent the spread of this disease. Understanding and addressing these risks is crucial for improving public health and food safety in Cameroon and the region of Africa.