Brugia

Brugia is a genus for a group of small roundworms. They are among roundworms that cause the parasitic disease filariasis.[1] Specifically, of the three species known, Brugia malayi and Brugia timori cause lymphatic filariasis in humans; and Brugia pahangi and Brugia patei infect domestic cats, dogs and other animals.[2][3] They are transmitted by the bite of mosquitos.[4]

Brugia
B. malayi from blood smear using Giemsa stain.
Scientific classification
Kingdom: Animalia
Phylum: Nematoda
Class: Chromadorea
Order: Rhabditida
Family: Onchocercidae
Genus: Brugia
Brugia, 1927
Species

Brugia malayi
Brugia timori
Brugia pahangi
Brugia patei

Discovery

The first species discovered was B. malayi. It was reported by a Dutch parasitologist Steffen Lambert Brug in 1927 from Southeast Asia (Malaya, for which the name was given). It was originally believed to be similar or closely related to another filarial roundworm then named Microfilaria bancrofti (now Wuchereria bancrofti), described by an English naturalist Thomas Spencer Cobbold in 1877. It was for this reason that Brug gave the original name Microfilaria (Filaria) malayi. Brug was aware of the difference mainly on the basis of their occurrence. He found both the worms in Sumatra, Java, Borneo, and Celebes; but in New Guinea only W. bancrofti was present, but not the new species.[5] They are so similar that even after a decade of research, there were still arguments of B. malayi as a separate and valid species. As such S. Sundar Rao and P.A. Maplestone assigned the name Wuchereria malayi in 1940.[6] The scientific name was retained for two decades.[7]

When a new species (now called Brugia pahangi) was discovered in 1956 from dog and cat, J. J. C. Buckley and J. F. B. Edeson named it Wuchereria pahangi after the village Pahang in Malay, where it was discovered.[8] Another species Wuchereria patei was described by Buckley, with G. S. Nelson and R. B. Heisch, in 1958. It was discovered from cats and dogs in Pate Island, Kenya.[9] Buckley reexamined all the Wuchereria species in 1960, and concluded that the genus should contain only W. bancrofti. He created a new genus Brugia in honour of the original discoverer, thus renaming B. malayi, B. pahangi, and B. patei.[10] In 1977, a new species B. timori was reported from Flores Island in Indonesia.[11]

Description

Brugia roundworms are small, measuring less than a centimetre. The longest female is 60 mm long and 0.19 mm wide, and male is 25 mm long and 0.1 mm wide.[10] Like other roundworms, the females are larger and longer than the males. The young ones called microfilariae are less than half a millimetre. They are enclosed in a sheath (egg shell) which are easily stained with Giemsa stain (but not for B. timori).[11] The sheath protects them while moving in the blood stream.[12] Species of Brugia are similar to W. bancrofti and Loa loa. But they can be differentiated from their smaller microfilariae, complex spicules, and fewer caudal papillae (typically 11, while it is 24 in W. bancrofti).[10]

Life cycle

Brugia roundworms complete their life cycle in two different hosts. Mosquitos are the intermediate host in which the young larvae develop, and thus they are also the vectors of filariasis. Different species of Mansonia and Aedes act as the intermediate hosts.[13] Humans (for B. malayi and B. timori), and animals (for B. pahangi and B. patei) acts as the definitive hosts in which the adult worms cause filariasis. The infective larvae called L3 (third stage) larvae are transmitted by an infected mosquito onto the skin of the definitive host. Once reaching the blood stream, they grow into adult roundworms. Male and female worms reproduce to release the young worms called microfilariae. These microfilariae move to peripheral blood stream from where they are picked up by another mosquito. Inside the mosquito, they became larvae, first L1 and then L3. The L3 larvae are stored in the proboscis from where they are ejected into the host during biting.[14][15]

References
  1. Sudomo, M; Chayabejara, S; Duong, S; Hernandez, L; Wu, WP; Bergquist, R (2010). "Elimination of lymphatic filariasis in Southeast Asia". Advances in Parasitology. 72: 205–233. doi:10.1016/S0065-308X(10)72008-X. PMID 20624533.
  2. Mak, JW; Navaratnam, V; Ramachandran, CP (1991). "Experimental chemotherapy of lymphatic filariasis. A review". Annals of Tropical Medicine and Parasitology. 85 (1): 131–137. doi:10.1080/00034983.1991.11812539. PMID 1888210.
  3. Vincent, Albert L.; Frommes, Stephen P.; Ash, Lawrence R. (1976). "Brugia malayi, Brugia pahangi, and Brugia patei: Pulmonary pathology in jirds, Meriones unguiculatus". Experimental Parasitology. 40 (3): 330–354. doi:10.1016/0014-4894(76)90100-4. PMID 976421.
  4. Townson, H; Chaithong, U (1991). "Mosquito host influences on development of filariae". Annals of Tropical Medicine and Parasitology. 85 (1): 149–163. doi:10.1080/00034983.1991.11812541. PMID 1888212.
  5. Brug, S. L. (1931). "Filariasis in Nederlandsch-Indie, III. Author(s)". Geneeskundig Tijdschrift voor Nederlandsche-Indie. 71 (3): 210–240.
  6. Rao, S.S.; Maplestone, P.A. (1940). "The Adult of Microfilaria malayi Brug, 1927". Indian Medical Gazette. 75 (3): 159–160.
  7. Wharton, R. H. (1957). "Studies on Filariasis in Malaya: Observations on the Development of Wuchereria Malayi in Mansonia (Mansonioides) Longipalpis". Annals of Tropical Medicine & Parasitology. 51 (3): 278–296. doi:10.1080/00034983.1957.11685817.
  8. Buckley, J. J. C.; Edeson, J. F. B. (1956). "On the Adult Morphology of Wuchereria sp. (malayi?) from a Monkey (Macaca irus) and from Cats in Malaya, and on Wuchereria pahangi n.sp. from a Dog and a Cat". Journal of Helminthology. 30 (01): 1–20. doi:10.1017/S0022149X00032922.
  9. Buckley, J. J. C.; Nelson, G. S.; Heisch, R. B. (1958). "On Wuchereria patei n.sp. from the Lymphatics of Cats, Dogs and Genet Gats on Pate Island, Kenya". Journal of Helminthology. 32 (1–2): 73–80. doi:10.1017/S0022149X00019362. PMID 13575807.
  10. Buckley, J. J. C. (1960). "On Brugia Gen. Nov. For Wuchereria Spp. of the Malayi Group i.e., W. Malayi (Brug, 1927), W. Pahangi Buckley and Edeson, 1956, and W. Patei Buckley, Nelson and Heisch, 1958". Annals of Tropical Medicine & Parasitology. 54 (1): 75–77. doi:10.1080/00034983.1960.11685959. PMID 13805587.
  11. Partono, F; Dennis, DT; Atmosoedjono, S; Oemijati, S; Cross, JH (1977). "Brugia timori sp. n. (nematoda: filarioidea) from Flores Island, Indonesia". The Journal of Parasitology. 63 (3): 540–546. JSTOR 3280019. PMID 864573.
  12. Shenoy, RK; Rakesh, PG; Baldwin, CI; Denham, DA (1996). "The sheath of the microfilaria of Brugia malayi from human infections has IgG on its surface". Parasitology Research. 82 (4): 382–384. doi:10.1007/s004360050132. PMID 8740559.
  13. Edeson, J. F. B.; Wilson, T. (1964). "The Epidemiology of Filariasis Due to Wuchereria Bancroft and Brugia Malayi". Annual Review of Entomology. 9 (1): 245–268. doi:10.1146/annurev.en.09.010164.001333.
  14. "Biology - Life Cycle of Brugia malayi". www.cdc.gov. U.S. Department of Health & Human Services. Retrieved 24 March 2017.
  15. Flockhart, HA; Denham, DA (1984). "Differentiation of species and life cycle stages of Brugia spp. by isoenzyme analysis". The Journal of Parasitology. 70 (3): 378–384. JSTOR 3281567. PMID 6238140.
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