Morphology, Life Cycle and Pathogenicity of Mansonella Ozzardi
Mansonella ozzardi is an arthropod-borne filarial nematode (roundworm). It is one of two filarial nematodes that cause serous cavity filariasis in humans. Mansonella perstans is the other filarial nematode that causes it in humans.
Mansonella ozzardi is an endoparasite that lives in the serous cavity of the human host’s abdomen. It is found in the mesenteries, peritoneum, and subcutaneous tissue.
Scientific Classification
Kingdom: Animalia
Phylum: Nematoda
Class: Secernentea
Order: Spirurida
Family: Onchocercidae
Genus: Mansonella
Species: M. ozzardi
Morphology of Mansonella ozzardi
M. ozzardi, like other nematodes, is a cylindrical, bilaterally symmetrical worm with a pseudocoel, or false body cavity. The cuticle on the parasite’s exterior is a protective layer that allows it to withstand the harsh environment of the human hosts’ digestive tracts.
Longitudinal muscles run along the body wall of M. ozzardi and other nematodes. These longitudinal muscles are also connected to dorsal, ventral, and longitudinal nerve cords.
Females are larger than males in the adult stages of M. ozzardi.
It is a dioecious species, with the female releasing a pheromone to attract males. When the male locates the female, he coils around her over the genital pore. During copulation, the male’s spicules are used to hold the female. The females have ovoviviparous eggs and the male sperm lacks a flagellum. It moves because of its amoeboid-like cell.
Life Cycle of Mansonella ozzardi
An arthropod (black fly or biting midge) will take a human blood meal and insert its filarial larvae into the human host.
The larvae will then mature into adults, inhabiting the peritoneal spaces and surrounding areas.
Adults will mate and give birth to unsheathed microfilariae. Microfilariae will enter the bloodstream.
An arthropod will consume microfilariae after ingesting blood from an infected human.
The microfilariae in the arthropod will travel from the midgut to the thoracic muscles.
The microfilariae will develop into first-stage larvae in the thoracic muscles.
Later, the microfilariae will mature into third-stage larvae.
The third-stage larvae will move from the thoracic muscles to the proboscis of the arthropod.
Symptoms of Mansonella ozzardi Infections
- Moderate fever
- Coldness in the legs
- Joint pains, like articular pain or arthralgias
- Headaches
- Pruritus (itchiness)
- Skin eruptions
- Pulmonary symptoms
- Lymphadenitis – inflammation of the lymph nodes
- Adenopathy – enlargement of the lymph nodes
- Hepatomegaly – enlargement of the liver.
M.ozzardi is also suspected of being the source of corneal lesions.
Mansonella ozzardi Infection Transmission
M. ozzardi is spread by two arthropods that feed on human blood: biting midges (genus Culicoides) and blackflies (genus Simulium). M. ozzardi’s intermediate host in the Caribbean is the biting midge. In the Amazon Basin and mainland South America, the black fly serves as an intermediate host for the filariae parasite.
Diagnosis/Treatment
A microscopic examination is used to identify the M. ozzardi microfilariae in blood samples from infected patients. To see the worms under the microscope, blood smears are usually stained with haematoxylin or Giemsa.
Microfilariae have been found in the skin, so doctors should not rely solely on blood samples. The presence of adult worms can be detected using ultrasound. The parasites in skin biopsies are currently being detected using a polymerase chain reaction-based method developed by researchers.
Because M. ozzardi harbors the endosymbiotic bacteria Wolbachia, doxycycline may be an effective therapy to eliminate adult worms. However, no trials with doxycycline (alone or in combination with ivermectin) for M. ozzardi infection have been conducted.
Mansonella ozzardi Infection Treatment
Ivermectin is the preferred treatment for M. ozzardi infections. It is a strong macrocyclic lactone that binds to chloride channels, allowing chloride ions to enter the affected cells. In M. ozzardi microfilariae, these cells hyperpolarize, resulting in muscle paralysis. This allows host immune cells to adhere to the surface of the microfilariae, facilitating their elimination. Adult worms are not killed by ivermectin.
Diethylcarbamazine (DEC) is another drug that has been used to treat filarial infections. While DEC is effective against many filarial parasites, it is ineffective against M. ozzardi microfilariae infections.
Methods of Disease Control
Individuals living in M. ozzardi-endemic areas can take preventive measures in addition to ivermectin.
Because biting midges cannot bite through clothing, residents of the Caribbean should wear long-sleeved shirts and pants to reduce the number of body parts exposed.
Insect repellents could also be used to cover exposed body parts that are not covered by clothing. Communities should also keep the natural vegetation around them in order to reduce the breeding grounds for biting midges.
In South America, the best way to control blackfly populations and M. ozzardi transmission is to apply insecticides designed specifically for blackfly larvae to streams and rivers.
When an insecticide is applied to a specific breeding site, it also kills larvae in breeding sites up to 10 kilometers downstream. Because blackflies can fly hundreds of kilometers with the wind, extensive networks of waterways must be treated with insecticide. Individuals should also avoid using waterways as much as possible.
