Encyclopedia of Parasitology

2016 Edition
| Editors: Heinz Mehlhorn

Isospora Species of Animals

  • Heinz Mehlhorn
Reference work entry
DOI: https://doi.org/10.1007/978-3-662-43978-4_3976


Greek: isos = identical; sporos = seed, spore; kystis = cyst, capsule.

Geographic Distributions/Epidemiology

The isospores are worldwide found as parasites of many groups of vertebrates. Their abundance in single infected hosts may reach very high numbers, as well as the rate of infection among given host population may reach 90 %.

Morphology/Life Cycle

In the present overlook only a few species are considered out of a number of several hundreds. The life cycle has the same phases (schizogony, gamagony, sporogony) like the   Eimeria species, which are as numerous. The difference is that in Isospora species the oocysts include two sporocysts with four sporozoites (Fig. 1), while in oocysts of Eimeria species four sporocysts with two sporozoites occur ( Coccidia). The oocysts are excreted in an unsporulated state and form their infectious stages in species-specific and temperature-dependent times outside of the host (=sporulation). Due to the extremely resistant oocyst wall the parasites inside can survive extreme conditions for years. Some examples of important Isospora species are listed in Table 1.
Isospora Species of Animals, Fig. 1

Two unsporulated oocysts of the genus Isospora (light micrograph)

Isospora Species of Animals, Table 1

Important Isospora species of animals



Size of oocysts (μm)

Prepatent period


I. suis

Pigs/Small intestine

17–22 × 17–19



I. canaria


13 × 10



I. erinacei

Hedgehogs/Small intestine

28–34 × 23–27



I. farahi


29 × 28



I. lacazei




I. lacerate


28 × 26



I. serini

Canaries/Intestine and its wall, liver, lung

12 × 10



Symptoms of Disease

Slight infections remain mostly symptomless. However, especially young animals suffer from diarrhea, which may be fatal due to huge loss of water. However, after surviving such an infection immunity protects them further on.


Isolation of oocysts (Figs. 1 and 2) by concentration methods ( S.A.F.C. M.I.F.G.,  flotation) from feces shows the species specific oocysts (compare Figs. 1 and 2 in   Cystoisospora species). The size and details of some species are listed in Table 1.
Isospora Species of Animals, Fig. 2

Sporulated oocyst of the genus Isospora containing two sporocysts each with four sporozoites (light micrograph)


Oral uptake of sporulated oocysts with fecally contaminated food.


Quick removement of animal feces from breeding sites.

Incubation Period

High variations in the different species: a few days until weeks.

Prepatent Period

Examples see Table 1.


Species specific: 1 to several weeks.


The medicament of choice is toltrazuril (10 mg/kg bodyweight) orally for 4–5 days.

Further Readings

  1. Berto BP (2011) Coccidia of New World passerine birds: a review of Eimeria and Isospora. Syst Parasitol 80:159–204CrossRefPubMedGoogle Scholar
  2. Box ED (1977) Life cycles of two Isospora species in the canary Serinus serinus. J Protozool 24:57–67CrossRefPubMedGoogle Scholar
  3. Mihalca AD (2009) A new species of Isospora in Ruppels agama with review of this genus in agamid lizards. Syst Parasitol 74:219–222CrossRefPubMedGoogle Scholar
  4. Milde K (1979) Light and electron microscopic studies on isosporan parasites in sparrows. Protistologica 15:607–627Google Scholar
  5. Worlicek HL (2009) Porcine coccidiosis. Investigations on the cellular immune response against Isospora suis. Parasitol Res 105:S151–S155CrossRefGoogle Scholar

Copyright information

© Springer-Verlag Berlin Heidelberg 2016

Authors and Affiliations

  1. 1.Institut für ZoomorphologieZellbiologie und Parasitologie, Heinrich-Heine-UniversitätDüsseldorfGermany