Brugia malayi is found in rural areas of Asia, in addition to isolated pockets in countries extending from the west coast of India to New Guinea, the Philippines and Japan. (Edington and Gilles, 1969)
Brugia malayi is an endoparasite that uses mosquitoes in the genus Mansonia in rural freshwater swamp forests in Southeast Asia as its intermediate host. In open swamp and irrigated fields and hill forests of South and East Asia, B. malayi uses the mosquitoes of the genera Mansonia, Aedes, Anopleles, and Culex. In the intermediate host, B. malayi occupies the stomach, thorax muscles, and the proboscis. When the mosquito bites a human, monkey, domestic cats, or forest carnivores, which are the only definitive hosts it enters the wound where it migrates to the lymphatic system through the blood stream were it remains throughout its adult life. (Anderson, 1992; Despommier, et al., 1995)
Adult Brugia malayi are long and slender with a smooth cuticle, kinked, and has a long cephalic space having a length:width ratio of about 2:1. The head is slightly swollen and has two circles of well-defined papillae. The tail of B. malayi is ventrally curved. Sexual dimorphism exists with the adult female B. malayi being approximately 8 cm long by 0.3 mm wide and the male about 2 cm long and 0.1 mm wide. (Strickland, 1991)
The reproductive cycle of B. malayi begins when a mosquito, the intermediate host which may include species in the genera Mansonia, Aedes, Anopleles, and Culex, acquires the sheathed microfilaria parasite in its blood meal. The microfilariae penetrate the gut wall of the mosquito where they lose their sheath and migrate to the muscles of the thorax. After 10 to 20 days, in which they undergo three molts, they develop into the infective third larval stage. Once the third larval stage is complete the B. malayi migrate to the proboscis of the mosquito. During the mosquito's blood meal the larvae enter the wound of the definitive host, which consist of humans, monkeys, domestic cats, and forest carnivores. The larvae then migrate through the subcutaneous tissue to the lymphatic vessels of the definitive host. Within about a year they develop into mature adults. The sheathed microfilariae produced after copulation, then enter the blood stream allowing the intermediate host to acquire the microfilaria repeating the cycle again.
In general, the worms molt before becoming adults, two molts occurring before they hatch from the eggs. Most all adult structures except certain reproductive parts are found in the young just before hatching. As adults, the worms will not molt, but can grow in size. (Anderson, 1992; Barnes, 1987; Despommier, et al., 1995)
Nematode females may produce a phermomone to attract males. The male coils around a female with his curved area over the female genital pore. The gubernaculum, made of cuticle tissue, guides spicules which extend through the cloaca and anus. Males use spicules to hold the female during copulation. Nematode sperm are amoeboid-like and lack flagella. (Barnes, 1987)
There is no parental investment beyond egg-laying.
A defining characteristic of B. malayi, as with all nematodes, is that they only have longitudinal muscles, therefore they exhibit an S-shaped motion during locomotion.
There are two forms of B. malayi, the periodic one, in which the microfilariae show a marked nocturnal presence in the blood (10 p.m. - 2 a.m.), and the subperiodic form in which the microfilariae are present throughout the day in the blood of the definitive host. The former is transmitted by species of Mansonia mosquitoes, which bite mainly at night in Southeast Asia, and use humans as the typical reservoir host. The later is found in South and East Asia and is transmitted by species of Mansonia, Aedes, Anopleles, and Culex mosquitoes that feed at any time of the day. (Anderson, 1992; Strickland, 1991)
Nematodes in general have papillae, setae and amphids as the main sense organs. Setae detect motion (mechanoreceptors), while amphids detect chemicals (chemoreceptors). (Barnes, 1987)
Brugia malayi feeds on blood and lymphatic tissue and fluid of its definitive host. (Anderson, 1992)
These parasites are probably not preyed on directly, but are ingested from host to host. Larval mortality is high as most of the parasites do not reach appropriate hosts.
Intermediate hosts include species in the genera Mansonia, Aedes, Anopleles, and Culex. During the mosquito's blood meal the larvae enter the wound of the definitive host, which consist of humans, monkeys, domestic cats, and forest carnivores.
The economic impact of B. malayi comes in the form of physical and mental disabilities. The physical disabilities come in the form of the inflammation of the lymph nodes, typically located from the waist and below, due to the blockage of the lymphatic circulation. This condition is often called elephantiasis due to the excessive inflammation and enlargment of the appendage. Because of the possible disfigurements, it can affect a person's quality of life and impair their ability to work. The mental disabilities primarily come in the form of depression due to society outcasting them because of their physical deformity. (Rauyajin, et al., 1995)
Renee Sherman Mulcrone (editor).
Kensey Amaya (author), University of Michigan-Ann Arbor, Teresa Friedrich (editor), University of Michigan-Ann Arbor.
living in landscapes dominated by human agriculture.
having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.
an animal that mainly eats meat
an animal which directly causes disease in humans. For example, diseases caused by infection of filarial nematodes (elephantiasis and river blindness).
uses smells or other chemicals to communicate
animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature
union of egg and spermatozoan
forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.
mainly lives in water that is not salty.
having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.
fertilization takes place within the female's body
marshes are wetland areas often dominated by grasses and reeds.
having the capacity to move from one place to another.
This terrestrial biome includes summits of high mountains, either without vegetation or covered by low, tundra-like vegetation.
the area in which the animal is naturally found, the region in which it is endemic.
found in the oriental region of the world. In other words, India and southeast Asia.
reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.
an organism that obtains nutrients from other organisms in a harmful way that doesn't cause immediate death
chemicals released into air or water that are detected by and responded to by other animals of the same species
rainforests, both temperate and tropical, are dominated by trees often forming a closed canopy with little light reaching the ground. Epiphytes and climbing plants are also abundant. Precipitation is typically not limiting, but may be somewhat seasonal.
remains in the same area
reproduction that includes combining the genetic contribution of two individuals, a male and a female
living in residential areas on the outskirts of large cities or towns.
a wetland area that may be permanently or intermittently covered in water, often dominated by woody vegetation.
uses touch to communicate
the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.
living in cities and large towns, landscapes dominated by human structures and activity.
uses sight to communicate
Anderson, R. 1992. Nematode Parasites of Vertebrates Their Development and Transmission. Oxon, UK: C.A.B. International.
Barnes, R. 1987. Invertebrate Zoology. Orlando Florida: Dryden Press.
Brusca, R., G. Brusca. 2003. Invertebrates. Sunderland, Massachusetts: Sinauer Associates, Inc..
Despommier, D., R. Gwadz, P. Hotez. 1995. Parasitic Diseases. Spriner-Verlag.
Edington, G., H. Gilles. 1969. Pathology in the Tropics. London, UK: Edward Arnold LTD.
Rauyajin, O., B. Kamthornawachara, P. Yablo. 1995. Socio-cultural and Behavioral Aspects of Mosquito-Borne Lymphatic Filariasis in Thailand: A qualitative Analysis. Soc. Sci. Med, 41: 1705-1713.
Strickland, T. 1991. Hunter’s Tropical Medicine. Philidelphia, PA: W.B. Saunders Company.