Understanding Moraxella catarrhalis

What is Moraxella Catarrhalis?

Moraxella catarrhalis (M. cataracta) is a parasitic protozoan organism that infects cats and humans. It causes feline calicivirus (FCV). FCV infection leads to severe clinical signs such as lethargy, vomiting, diarrhea, dehydration and sometimes death. The disease usually occurs in the late spring or summer months when temperatures are high and humidity low. Cats become infected through direct contact with other animals or contaminated water sources. Humans acquire it from drinking contaminated water or eating undercooked meat.

The parasite lives in the intestinal tract of its host and produces eggs which hatch into larvae. These larvae move around inside the body until they reach the lungs where they mature and release spores that cause infection in humans. There are three species of M.

catarrhalis: F. catteri, F. felis and F. luteus. They infect different mammals including humans, domestic dogs, horses, cows and goats but not birds or reptiles such as snakes or lizards.

How does Moraxella Catarrhalis Infect Humans?

Infection occurs through ingestion of fecal matter containing the parasite’s eggs or feces. In addition, it’s possible to inhale infected particles of saliva containing the parasite eggs. In both cases, humans become susceptible to infection when they are in an environment contaminated with these materials.

Symptoms of an M. catarrhalis infection include:




Watery eyes

Pus in eyes and nose

Nasal congestion

Diarrhea (in children)

Ear pain (otitis media) and discharge from ears

Fever and general malaise

Skin rashes

How is Moraxella Catarrhalis Treated?

Antibiotics such as erythromycin, sulfamethoxazole with trimethoprim, or chloramphenicol can be used to treat the infection. The choice depends on the type of organism identified in a lab test. Antibiotics must be taken for at least 10 days.

In some cases, a chest X-ray is taken to rule out any complications such as pneumonia or an acute asthma attack.

Complications from untreated M. catarrhalis infection may include:


Nasal and sinus blockage

Infection of the ear canal (otitis media) resulting in hearing loss or dizziness, or meningitis

Infection of the brain (encephalitis) causing drowsiness, fever, disorientation, coma and even death

How is Moraxella Catarrhalis Spread?

M. catarrhalis spreads through direct contact with infected individuals or contact with contaminated objects or materials.

Infected children can spread the infection to other children in the classroom. Since these children are usually not aware that they are infected, the infection can spread quickly even in a relatively small community.

The disease is also spread by handling infected cats or from touching their feces and then touching your eyes, nose or mouth before the hands have been washed.

Cleanliness and good handwashing habits help stop the spread of Moraxella Catarrhalis.

How Prevalent is Moraxella Catarrhalis?

Moraxella Catarrhalis is the most common cause of otitis media (middle ear infection) in children. It accounts for about 20 percent of all ear infections.

Moraxella Catarrhalis is the most common cause of sinusitis in adults. It’s one of the most common causes of human respiratory tract infection and a leading cause of sore throat.

The vast majority of Moraxella Catarrhalis cases are acquired from cats. The organism is commonly found in the upper respiratory tracts of felines.

How can Moraxella Catarrhalis be Prevented?

Sources & references used in this article:

Towards understanding the functional role of the glycosyltransferases involved in the biosynthesis of Moraxella catarrhalis lipooligosaccharide by IR Peak, ID Grice, I Faglin, Z Klipic, PM Collins… – The FEBS …, 2007 – Wiley Online Library

Middle Ear Mucin Glycoprotein: Purification and Interaction with Nontypable Haemophilus Influenzae and Moraxella Catarrhalis by MS Reddy, TF Murphy, HS Faden… – … –Head and Neck …, 1997 – journals.sagepub.com

Molecular aspects of Moraxella catarrhalis pathogenesis by SPW de Vries, HJ Bootsma, JP Hays… – Microbiology and …, 2009 – Am Soc Microbiol

Moraxella catarrhalis: a review of an important human mucosal pathogen by R Karalus, A Campagnari – Microbes and infection, 2000 – Elsevier