Page 192 - The Veterinary Laboratory and Field Manual 3rd Edition

Parasitology 161

are collected. If there is to be a delay in examina- taken from rectal scrapings or from mucus on
tion these samples should be stored at 4°C. In the surface of faecal material from infected
most cases, coccidial oocysts (‘eggs’) present in animals; whereas, cysts can be easily observed
the faeces will be detected during routine exami- using a ZnSO float.
4
nation for helminths using flotation techniques. Haemoparasitic protozoa are another impor-
Most oocysts are easily seen using medium mag- tant group that can have serious effects on
nification (20×) under the microscope but are livestock health, these include Babesia sp.,
smaller than most helminth eggs. Identification Theileria sp. and trypanosome species which are
of the coccidial species present may require transmitted by vectors such as ticks and/or biting
sporulation (development to the next stage of insects. Anaplasma sp. are not protozoa but are
the life cycle, see Figure 3.31a) before identi- often considered along with this group as they
fication can be completed, this requires freshly also parasitize blood cells and are transmitted
collected material. Trophozoites of Entamoeba by ticks and biting insects. Anaplasma sp. are
sp. and Giardia sp. may be seen in fresh smears rickettsia and are briefly mentioned in Chapter 4.

(a) (b)

Figure 3.31 (a) The life cycle of Eimeria sp. Protozoal organisms of the genus Eimera or Cystoisospora
cause ‘coccidiosis’ in a number of species, in most cases the species of coccidia is host specific. The life
cycles of protozoal species tend to be quite complex with various names for different stages of the life cycle.
(A) Oocyst released in the faeces of the definitive host. (B) Sporulation of oocyst and formulation of sporo-
cysts. (C) Each sporocyst divides to form two banana shaped sporozoites. (A)–(C) is known as ‘sporogony’.
(D) Intestinal epithelial cells with nuclei illustrated. (E) Release of sporozoites and invasion of intestinal
cells. (F) Formation of first stage schizont and release of merozoites. (G) Schizogony (asexual reproduction).
(H) Formation of second stage schizont. (H)–(M) is known as ‘gametogony’. (I) Microgametocyte (male),
(J) release of microgametes, (K) macrogametocyte (female), (N) microgametes (male) enter a macroga-
mete (female) and a zygote (M) is formed. (b) Photograph of Cystoisospora sp. Photo: Dr Susan Kutz,
University of Calgary, Canada.

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