How many lice are there? - briefly
Estimates indicate that billions of lice exist globally, with roughly 300 million human infestations occurring at any given time.
How many lice are there? - in detail
The global lice population can be expressed in several distinct categories, each with its own estimated magnitude.
Human head lice (Pediculus humanus capitis) affect roughly 6 % of the world’s 8 billion people, resulting in an estimated 480 million individual infestations. Assuming an average of 10 adults per infestation, the total number of head lice reaches approximately 4.8 billion.
Body lice (Pediculus humanus humanus) are less common, occurring primarily in populations with limited access to hygiene facilities. Epidemiological surveys indicate a prevalence of about 0.5 % among the global population, corresponding to 40 million infestations. With an average colony size of 30 adults, the total body‑lice count approaches 1.2 billion.
Pubic lice (Pthirus pubis) have a reported prevalence of 0.1 % worldwide, equating to 8 million infestations. Typical colonies contain roughly 20 adults, yielding an estimated 160 million pubic lice.
Animal lice encompass a broad range of species that parasitize mammals, birds, and reptiles. Veterinary studies estimate that domestic livestock host an average of 15 lice per animal. With approximately 1.5 billion livestock individuals globally, the animal‑lice population is close to 22.5 billion. Wild‑animal hosts add an additional estimated 10 billion lice, based on surveyed wildlife densities.
Summarized estimates:
- Head lice: ≈ 4.8 billion
- Body lice: ≈ 1.2 billion
- Pubic lice: ≈ 160 million
- Livestock lice: ≈ 22.5 billion
- Wild‑animal lice: ≈ 10 billion
Combined, the total number of lice inhabiting humans and animals worldwide exceeds 38 billion individuals. These figures derive from prevalence surveys, average colony sizes, and global population data, providing a comprehensive quantitative picture of the parasite’s abundance.