Page 195 - The Veterinary Laboratory and Field Manual 3rd Edition

164 Susan C. Cork and Mani Lejeune

prevention. Diseases caused by ‘blood protozoa’ past few decades – this is partly the result of
and other haemoparasites of ruminants will be molecular phylogenetics but it also reflects our
considered in Section 3.6. better understanding of the complex life cycles
of protozoal parasites. Table 3.6b outlines one
current taxonomic list of protozoa of veterinary
coccidiosis importance.
The life cycle of Eimeria sp. is often represen-
Coccidiosis is a general term used to refer to tative of the coccidial group and other life cycles
clinical disease caused by a number of protozoal are compared with it (Figure 3.31a). Typically
organisms in the class Coccidia. The species there are two main phases of reproduction in
of veterinary importance fall into two distinct the life cycle: asexual and sexual. Asexual stage
families, the Eimeridae and the Sarcocystidae. occurs following ingestion of infective sporulated
The term ‘coccidiosis’ in poultry and other live- oocysts. The sporozoites from oocysts emerge
stock is usually reserved for diseases caused by
Eimeria sp. and/or Isospora sp. Eimeria sp. occur
in poultry, ruminants, pigs, horses and rabbits, Table 3.7 Some coccidial protozoa
and typically cause disease following invasion of and their hosts.
intestinal epithelial cells, see Figure 3.30. Some
species also invade the epithelial cells in the Species Host
kidney and liver. Most species are host specific. Eimeria tenella, E. necatrix, E. brunetti, Chickens
Some of the most common species are outlined E. maxima, E. acervulina, E. praecox,
in Table 3.7. The life cycles of Isospora sp. and etc.
Eimeria sp. have many similarities, but differ Eimeria meleagrimitis, E. adenoeides, Turkeys
in a number of respects. The organisms can be etc.
identified in faecal samples by the morphology Eimeria zuerni, E. bovis, Cattle
of their oocytes. Isospora sp. have sporulated E. canadensis, E. auburnensis,
E. alabamensis, E. ellipsoidalis,
oocysts which contain two sporocysts each with E. cylindrica, E. bukidnonensis, etc.
four sporozoites whereas sporulated oocysts Eimeria ovinoidalis, E. ahsata, E. Sheep
of Eimeria sp. tend to contain four sporocysts bakuensis, E. crandallis, E. parva,
with two sporozoites. Some species of Isospora E. intricata, E. granulosa, E. faurei, etc.
have extra-intestinal stages occurring in the Eimeria ninakohlyakimovae, Goats
liver, spleen and lymph nodes which then may E. arloingi, E. christenseni, E. caprina,
re-infect the intestinal mucosa. In some cases, E. hirci, E. parva, E. aspheronica, etc.
rodents may ingest oocysts from carnivore Eimeria intestinalis, E. steidae (liver) Rabbits
Isospora sp. and become infected with the asexual Eimeria leuckarti Horses
stages of the parasite, the rodents then act as Eimeria debliecki, E. perminuta, Pigs
reservoir hosts and dogs and cats are re-infected E. spinosa, E. scabra, E. porci,
when ingesting infected rodents. These species E. neobeliecki, Cystoisospora suis
of Isospora that involve a reservoir/transport/ Cystoisospora felis, C. rivolta, Cats
paratenic hosts are now classified under the Toxoplasma gondii, Sarcocystis sp.,
genus Cystoisospora. The genus Isospora once etc.
included species now in the genera Toxoplasma, Cystoisospora canis, C. ohioensis, Dogs
Besnotia and Sarcocystis. The nomenclature for Neospora caninum, Sarcocystis sp.,
many protozoal organisms has changed over the etc.

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