Page 118 - parasitology for medical and clinical laboratoryprofessionals

98 CHAPTER 4

TABLE 4-5 Parasitic Species Producing Filariasis

LYMPHATIC FILARIASIS SUBCUTANEOUS FILARIASIS SEROUS CAVITY FILARIASIS
Wucheria bancrofti Onchocerca volvulus Mansonella perstans

Brugia malayi Loa loa Mansonella ozzardi
Brugia timori Mansonella streptocerca
Dracunculus medinensis

Species of Causative Organisms
for Filariasis

These species are divided into three groups according to
the tissues and cavities of the body they impact upon and
occupy, as shown at the top of the page.
The life cycles, the transmitting vectors, and Source: Centers for Disease Control and Prevention (CDC)
in particular the tissues affected by these organisms,
dictate the category into which they are placed.
The worms that cause lymphatic filariasis are found
chiefly in the lymphatic system, including the lymph
nodes, and in chronic cases these worms lead to the
disease called elephantiasis. Subcutaneous filariasis FIGURE 4-15 Simulium sp. of flies, or “blackflies,” a
caused by Loa loa (the African eye worm), Mansonella vector of the disease, onchocerciasis, or “river blindness”
streptocerca, Onchocerca volvulus, and Dracunculus
medinensis (the guinea worm) result in invasions by
the small worms or filaria of areas just beneath the skin, of South America, Southeast Asia, and a few other areas
including the layers of tissue in the eye in the case of of the world harbor most of the filarial diseases. Filari-
Loa loa and the fatty layers slightly deeper in the organ. asis is often disabling and certainly figuratively damag-
Onchocerciasis is the term for “river blindness” and ing for many, but the disease is rarely fatal. However, it
the chief vector of the organism responsible for this is one of the leading causes of both permanent and long-
condition is the Simulium sp. of flies, or “blackfly” standing disability throughout the world. In 2002, an
(Figure 4-15). Serous cavity filariasis caused by the ambitious program to rid the world of six diseases within
worms Mansonella perstans and Mansonella ozzardi 20 years was undertaken by a number of organizations.
occupy the serous cavity of the abdomen that results in The WHO, the Bill and Melinda Gates Foundation, the
pronounced distension of the stomach. In all categories Carter Center, and the International Task Force for Dis-
the transmitting vectors are either bloodsucking insects ease Eradication (ITFDE) united their efforts to accom-
(fly or mosquito) or copecod crustaceans in the case of plish this worthy goal, toward which some modest gains
Dracunculus medinensis. have been achieved.
Along with lymphatic filariasis, five other diseases
Epidemiology of Filariasis are earmarked as having the probability of becoming ex-
tinct within two decades. The remaining five potentially
It is probable that up to 170 million people in mostly eradicable diseases, with the exception of the viral dis-
tropical and subtropical areas suffer from some sort of fi- ease of polio, are all parasite infections and are identified
lariasis, as there are several species which cause this dis- as targets of these efforts. They include the guinea worm,
ease. The continent of Africa, islands of the Pacific, areas polio, trachoma, schistosomiasis, and river blindness