Leprosy in wild chimpanzees

Area of Science:

• Zoological medicine
• Primate health
• Infectious diseases

Background:

• Humans are the primary host for Mycobacterium leprae, the causative agent of leprosy.
• Spillover events have established leprosy in maintenance hosts like armadillos and red squirrels.
• Naturally acquired leprosy in captive nonhuman primates has been documented, but infection origins remain unclear.

Purpose of the Study:

• To investigate leprosy-like lesions in wild western chimpanzee populations.
• To identify the causative agent and its genetic characteristics in affected chimpanzees.
• To understand the potential for Mycobacterium leprae circulation in wild primate populations.

Main Methods:

• Longitudinal monitoring of wild chimpanzee populations in Guinea-Bissau and Côte d'Ivoire.
• Screening of faecal and necropsy samples for Mycobacterium leprae.
• Phylogenomic comparison of chimpanzee M. leprae strains with known human and animal strains.

Main Results:

• Leprosy-like lesions and disease progression were observed in two wild western chimpanzee populations.
• Mycobacterium leprae was confirmed as the causative agent in affected chimpanzees.
• Chimpanzee M. leprae strains belonged to rare genotypes (4N/O and 2F), distinct from common human and animal strains.

Conclusions:

• Wild chimpanzees are susceptible to leprosy, presenting clinical signs compatible with advanced disease.
• Mycobacterium leprae circulates in wild chimpanzee populations, suggesting broader wildlife involvement in leprosy transmission.
• The findings indicate potential exposure to humans or unknown environmental sources for M. leprae in wildlife.