Mansonella ozzardi
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| Mansonella ozzardi | |
|---|---|
Scientific classification  | |
| Kingdom: | Animalia |
| Phylum: | Nematoda |
| Class: | Chromadorea |
| Order: | Rhabditida |
| Family: | Onchocercidae |
| Genus: | Mansonella |
| Species: | M. ozzardi |
| Binomial name | |
| Mansonella ozzardi Manson, 1897 | |
Mansonella ozzardi is a filarial (arthropod-borne) nematode (roundworm). This filarial nematode is one of two that causes serous cavity filariasis in humans. The other filarial nematode that causes it in humans is Mansonella perstans. M. ozzardi is an endoparasite that inhabits the serous cavity of the abdomen in the human host. It lives within the mesenteries, peritoneum, and in the subcutaneous tissue.
Like other nematodes, M. ozzardi is a cylindrical and bilaterally symmetrical worm, with a pseudocoel, or a false body cavity. The exterior of the parasite, the cuticle, is a protective layer that can withstand the harsh environment in the digestive tracts of the human hosts.
Mansonella ozzardi and other nematodes have longitudinal muscles that run along the body wall. They also have dorsal, ventral, and longitudinal nerve cords connected to these longitudinal muscles.
In the adult stages of M. ozzardi, the females are larger than the males.
Mansonella ozzardi is usually smaller than those Onchocerca Volvulus (that causes human onchocerciasis) when both species co-exist; especially in some rural areas in Brazil, within the Amazonian onchocerciasis focus.
Reproduction
This is a dioecious species; the female is believed to release a pheromone to attract males.[1] When the male finds the female, he will coil around the female over the genital pore. The male's spicules are used to hold the female during copulation. The females are ovoviviparous. The sperm of a nematode lacks a flagellum. Its motility is due to its amoeboid-type cell.
Geographic range
This is a New World parasite. It is prominent in the subtropical, tropical, and temperate regions of Central and South America (Mexico, Panama, Brazil, Colombia, and Argentina), and the Caribbean.[2] The prevalence of M. ozzardi in Brazil is very high; about 44–52% of Brazilian farmers are infected. It is also prevalent with the American Indian population. Many transmission hotspots in the Amazon Basin map to indigenous communities. Endemicity levels vary widely among rural villages, situated a few kilometers apart along the same rivers in the western Amazon Basin of Brazil.[3]
Lifecycle
- An arthropod (black fly or biting midge) will take a blood meal from a human and will insert its third-stage filarial larvae into the human host.
- The larvae will then become adults and will inhabit the peritoneal spaces and adjacent locations.
- The adults will mate and produce unsheathed microfilariae. These microfilariae will go to the bloodstream.
- An arthropod will take a blood meal from an infected human and ingest the microfilariae.
- In the arthropod, the microfilariae will travel from the midgut to the thoracic muscles.
- In the thoracic muscles, the microfilariae will develop into the first-stage larvae.
- Later, the microfilariae will further develop into the third-stage larvae.
- The third-stage larvae will travel from the thoracic muscles to the arthropod's proboscis. This is the stage where the arthropod can infect a human when it takes a blood meal.
Transmission
Mansonella ozzardi is transmitted by two types of arthropods that feed on the blood of humans: biting midges (genus Culicoides) and blackflies (genus Simulium). In the Caribbean, M. ozzardi uses the biting midge as its intermediate host. The black fly serves as the intermediate host for the filariae parasite in the Amazon Basin and mainland South America.
Biting midge
The biting midges are small flies that breed on sandy beaches near the sea. Some species also lay their eggs on decaying leaf litter, humus, manure, and partially rotten vegetation, in tree holes, and the cut stumps of banana trees. They feed on the blood of mammals, birds, reptiles, and humans. Their short mouthparts prohibit them from biting through clothing. As a result, they prefer to feed on the head or other exposed body parts. Blood meals occur throughout the day and night, but biting activity peaks during the early evening. Since individual bites can be painful, they are a cause of concern because they tend to attack in swarms of hundreds or thousands. Due to their small size, they can pass through mesh mosquito nets.
Black fly
The blackflies are larger blood-sucking flies that breed in fast-flowing streams and rivers. Their larvae can be found attached to submerged vegetation and stones of infected waterways. Blood meals occur during the day in the outdoors, especially along riverbeds. After a meal, the flies rest for 2–3 days on trees and other vegetation to digest the blood. Like the biting midges, blackflies attack their victims in swarms and their bites are painful. The bites may cause swelling, inflammation, and irritation that may last for weeks.[4]