Page 296 - parasitology for medical and clinical laboratoryprofessionals

276 CHAPTER 12

PROCEDURE 12-5

(continued)

Identification Procedures for Other Blood Parasites

Four species of Trypanosoma may be found in human blood (Table 12-4).
As with malaria, travel to endemic areas for non-malarial infections aids in identi-
fication of the parasite. Trypanosoma brucei is the hemoflagellate that causes sleep-

ing sickness. It is spread by the bite of the tsetse fly requiring travel to the “tsetse
belt” of sub-Saharan Africa where the organism is transferred from a host such as a
cow or other grazing animal. The disease is endemic to Africa and two geographically
isolated strains are known. It is also possible to find other parasites, including try-

panosomes, microfilaria, Babesia spp., and Leishmania on the blood smears stained
by the procedures outlined here. If parasites are not found in the initial blood speci-
men/smears, it is advisable to take additional thick and thin smears every 6 to 8 hours,
for as long as 48 hours if necessary, regardless of the parasite suspected.

Filariasis Detection
For cases of blood parasites where microfilariae would be in the blood, initial scan-

ning of a stained smear at 10-power should reveal the presence of this form of para-
site. Patient history including travel is also help ful. If filariasis is probable based on

the clinical history, both diurnal (day) and nocturnal (night) collections of blood are
necessary to allow for differences in the activity of the various species.

TABLE 12-4 Species of blood parasites, how they are transmitted and the diseases caused

ORGANISM TRANSMISSION DISEASE CAUSED
Plasmodium spp. Mosquito bite Malaria
Babesia Tick bite Babesiosis
Trypanosoma brucei Tsetse fly bite African sleeping sickness,
trypanosomiasis
Trypanosoma cruzi Reduviid bug bite contaminated with Chagas disease, American
bug’s infected feces trypanosomiasis
Wuchereria bancrofti Mosquito bite Filariasis, elephantiasis

Brugia spp. Mosquito bite Filariasis, elephantiasis
Leishmania donovani Sand fly bite Visceral leishmaniasis, Kala azar,
dumdum fever
Toxoplasma gondii Ingestion of oocysts, eating under- Toxoplasmosis
cooked infected meat, congenital