2018 anthrax outbreak in Uganda tied to infected cow meat, study finds

By Dr. Ananya Mandal, MDDec 1 2020

On April 18, 2018, 7 suspected human anthrax cases were reported from the Kween District Health Office in Kween District, Uganda. Ugandan researchers from the Uganda Public Health Fellowship Program, Kampala, Uganda, have now published their findings on the outbreak's source in the latest issue of the CDC's (Centre for Disease Prevention and Control) Emerging Infectious Diseases.

Anthrax

Anthrax is a bacterial disease caused by Bacillus anthracis, a type of gram-positive, spore-forming bacteria. It is an infection of animal origin (also known as a zoonotic infection). The bacteria are capable of lying dormant in the form of spores in carcasses and burial grounds of infected animals. Annually 2,000 to 20,000 cases of anthrax are seen around the world. Several regions in sub-Saharan Africa and Asia have frequent outbreaks of infection.

Bacillus anthracis, gram-positive spore-forming bacteria which cause anthrax (3D illustration). Image Credit: Kateryna Kon / Shutterstock

The infection occurs in humans who come in contact with infected animals or their carcasses or animal products. These animal products include "hair, wool, hides, bones," the authors wrote. The infection is also spread by breathing in spores of the bacteria.

With anthrax, there are four forms of infection:

• Skin or cutaneous form – the incubation period is between 1 and 12 days. 95 percent of the cases take this form, which is most often associated with handling and consuming infected animals
• Inhalational form – this has an incubation period between 1 and 60 days and occurs when the bacteria are breathed in
• Gastrointestinal form – this has an incubation period between 1 and 6 days and is associated with handling and consuming infected animals
• Injected infection – this has an incubation period between 1 and 10 days

Background

In April, 2018, a suspected anthrax outbreak was detected in the Kween District of Uganda by the Ministry of Health. A total of 49 cases were identified, of which 3 were confirmed, and 46 were suspected. No deaths occurred. Seven suspected cases of cutaneous anthrax from 2 neighboring villages, Kaplobotwo and Rikwo, were identified.

This study was conducted to investigate the anthrax outbreak scale, its spread and exposures and any preventive measures that could be taken to contain any further spread.

Exposure to cow meat

The researchers write that they could connect the suspected anthrax cases with multiple exposures to handling the carcass of a cow that had died suddenly. Most of these cases were cutaneous anthrax.

They also found that eating infected cow meat was associated with gastrointestinal anthrax. They noted that eating undercooked meat, in particular, was significantly associated with gastrointestinal anthrax. When the meat was boiled for over an hour, however, the risk of gastrointestinal anthrax was considerably reduced.

Study: Outbreak of Anthrax Associated with Handling and Eating Meat from a Cow, Uganda, 2018. Image Credit: Tatsiana Hendzel / Shutterstock

Case definition of anthrax

Cutaneous anthrax

The team defined a case of cutaneous anthrax as the presence of a skin lesion or "vesicle or eschar" alongside more than 2 signs and symptoms over the skin such as itching, redness and swelling or one sign or symptom over the skin along with lymph node swelling.

Gastrointestinal anthrax

The team defined a case of gastrointestinal anthrax as 2 or more signs or symptoms of acute origin, including "abdominal pain, vomiting, diarrhea, or sore throat."

Once symptoms were identified, the suspected case was followed up. A clinical specimen such as blood or swab from a skin lesion or vesicle was tested for B. anthracis by real-time PCR (rPCR).

Cases were obtained from three health facilities around the outbreak region, including Ngenge Health Center III and two private clinics. A total of 57 households in two villages were surveyed for possible cases.

Findings

A total of 49 cases of human anthrax were found. Of these, 3 were confirmed by rPCR testing. The average age of the patients was 30 (ranging between 1 and 89 years of age). There were:

• 13 or 27 percent with cutaneous anthrax only
• 16 or 33 percent with gastrointestinal anthrax only
• 20 or 41 percent had both cutaneous and gastrointestinal anthrax. Symptoms included "photophobia, neck pain or stiffness," which meant the involvement of the meninges.
• No deaths were reported

Recommendations

The researchers recommend the following measures to prevent an outbreak and prevent the spread of infection:

• Provide antibiotics after persons have been exposed to infected cow meat (ciprofloxacin and doxycycline)
• Vaccinating all healthy livestock with anthrax vaccines in an around the affected areas
• Boiling meat for over 60 minutes can kill anthrax spores. According to World Health Organization guidelines, "any animal that is sick, behaves strangely or has died suddenly should not be used for food or for making any product, as it may have succumbed to an infectious disease"
• All persons need to be educated regarding avoidance of handling or eating meat from livestock that had died of unknown causes and that these animals could carry anthrax
• Farmers and animal handlers need better education regarding the safe handling and disposal of animal carcasses. The authors of the study wrote, "For burial, carcasses should be disinfected at the site of death with 12.5% formalin solution and buried in a pit >6 feet deep with the bottom of the pit ≥3 feet above the water table."