Sunday, September 21, 2014

Loa loa - African Eye Worm

Wednesday, September 10, 2014

Loa loa - African Eye Worm




Author: Natalie Ameral

Photo Courtesy of workforce.calu.e


          Taxonomy 

(Animal Diversity Web, 2014):
    Domain: Eukarota
        Kingdom: Animalia
    Phylum: Nematoda
    Class: Secernentea
        Order: Spirurida
        Family: Filariidea
        Genus: Loa
        Species: loa


 


 

Scientific and common name:

       Unfortunately, this nematode gets its name from the area in which it resides as a parasite in the human body: the eye. Shortly after the discovery of this nematode in 1770, in 1778 these worms were found in the eyes of slaves being transported via ship (Borg, 2007). Currently, this infestation of the eye is most commonly found on the Atlantic side of Africa, specifically surrounding the Gulf of Guinea (Borg, 2007).


 

Ecology:

Loa loa has found a fantastic niche for itself in the tropical rain forest and savanna biomes of coastal west Africa (Kelly-Hope et.al, 2012). 


PLOS website - Hope-Kelly 2012

 The graph above is by far the best indicator of Loa loa distribution. The x axis represents the western, central, and eastern regions of the Congo river system in all the graphs. Elevation is measure in meters, NDVI is vegetation, precipitation is measured in millimeters, temperature in degrees Celsius, and humidity in specific humidity. Interestingly, different variable are more suitable for different locations. For example, a lower temperature is selected for in the east as opposed to a higher temperature in the center. This variation may make it easier for people to decide where to live and farm if Loa loa is a concern of theirs.     


Physical description and life cycle:


According to Borg (2007), worms range from 2 cm to 7 cm in length, females being longer than males. Comparatively, this is quite large for most nematodes. Borg also explains the life cycle of Loa loa. Most of the life processes take place in the human body host. Larva grow under the skin and once mature lay eggs. These eggs have been found in blood, urine, and spinal fluid. 


Interesting trivia:


Loa loa do not make it into the human blood stream on their own. The middle man of the infestation process is the mango fly (Borg, 2007). The larvae first make their journey into a human host via a bite made by the mango fly (Borg, 2007). This bite contains larvae that will use the host to grow and become adult worms (Borg, 2007). Once the adult worms lay their eggs, another Mango fly may come along, bite the human, and ingest these larvae (Borg 2007). The larvae are then deposited into another human via another bite (Born 2007). 


References:
  • Myers, P., R. Espinosa, C. S. Parr, T. Jones, G. S. Hammond, and T. A. Dewey. 2014. The Animal Diversity Web (online). Accessed at http://animaldiversity.org.
  • Borg L. 2007. http://web.stanford.edu/group/parasites/ParaSites2006/Loiasis/Index.html
  • Kelly-Hope Louise A. et al. June 26, 2012. Loa loa Ecology in Central Africa: Role of the Congo River System. Public Library of Science. http://www.plosntds.org/article/info%3Adoi%2F10.1371%2Fjournal.pntd.0001605

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