Protozoal
enteritis: Coccidiosis
Esther van
Praag, Ph.D.
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Coccidiosis is a highly contagious sporozoal infection in rabbits, with low prognosis of
healing. It is caused by a protozoal parasite, Eimeria
sp.. As many as 25 species of coccidia have been observed in the gastrointestinal tract
of the rabbit; it should, however, be noted that in some cases, one and the
same coccidia has been given several names. Eimeria sp. parasites are highly host, organ and
tissue specific and do rarely represent a zoonotic danger for human beings.
Healthy rabbits can be asymptomatic
"carriers" of the protozoa. The oocysts (eggs),
shed with the feces, will contaminate the environment, food and water.
Although the disease occurs essentially in intensively managed animals,
especially younger ones, it appears also in well cared for rabbits. General
hygienic measures indicate that rabbits should be given a dry rather than
moist pellets, washed fresh vegetables and plenty of fresh water; in these
conditions coccidiosis in unlikely to appear. When several rabbits are housed
together, it is recommended to avoid putting food on the ground or to let
several rabbits eat each other’s soft cecals. The parasite has a life-cycle, which
lasts 4 to 14 days. It starts after oral ingestion of food contaminated by
oocysts. The oocyst wall will be broken down in the stomach and spores will
be released. The presence of biliary and pancreatic enzymes in the duodenal
portion of the intestine stimulates the spores.
After
actively entering the cells lining the intestinal wall, the spore will start
to divide asexually during one or more stages (schizogony).
"Merozoites" (stage of development) will
be released to infest other cells of the intestinal mucosa. The final stage
of schizogony leads to the formation of gametes,
enabling sexual reproduction. Oocytes are shed in the feces. The
asexual and sexual stages differ often in their location, organ and tissue
specificities. The presence of coccidoa
will affect the hosting cell; some are inhibited in their function, other are hypertrophied. Induced villi atrophy will lead to
malabsorption of nutrients, electrolyte disbalance,
anemia, hypoproteinemia, and dehydration due to the
epithelial erosion and ulceration.
Clinical signs
The
severity of coccidiosis depends on the number of ingested oocytes. Clinical
signs are reduced appetite, depression, abdominal pain and pale watery mucous
membranes, but they can be absent in older rabbits. Inspection of the feces
often reveals blood and threads of mucus. Young rabbits present a retarded
growth, due to side effects on the kidney and the liver in particular. Hematological
studies show a reduced hemoglobin and RBC count, accompanied by a significant
increase of PCV and total WBC. Serum analysis show decreased levels of sodium
and chloride, and increased levels of potassium. This electrolyte disbalance can be attributed to diarrhea. Serum calcium,
iron, copper, zinc, and glucose are usually slightly lower than in healthy
animals and may indicate malnutrition due to intestinal damage, or secondary
bacterial infection. Liver coccidiosis is accompanied by significant
elevation of serum bilirubin, alkaline phosphatase (ALP), alanine
aminotransferase (ALT) and aspartate aminotransferase (AST), and gamma glutamyl transpeptidase (GGT).
Values return to normal after appropriate treatment. See: Clinical blood biochemistry of the
rabbit Intestinal coccidiosis The intestinal form of coccidiosis mainly
affects youngsters from the age of 6 weeks to 5 months and is attributed to
stress, noise, transport or immunosuppression. It is mainly observed in young
newly weaned rabbits, but is also found in older rabbits.
Symptoms
are a rough coat, dullness, decreased appetite, dehydration, loss of weight
and (profuse) diarrhea, 4 to 6 days post-infection. If the loss of weight
reaches 20%, death follows within 24 hours. It is preceded by convulsion or
paralysis. During necropsy, inflammation and edema are found in the ileum and
the jejunum portions of the intestine. It is sometimes accompanied by
bleedings and mucosal ulcerations. Hepatic coccidiosis The
liver form of coccidiosis affects rabbits of all ages. It is characterized by
listlessness, thirst, enlarge, and wasting of the back and hindquarters, with
enlargement of the abdomen. On abdominal X-rays, the liver and liver and gall
bladder appear enlarged. This
form of coccidiosis runs either as a chronic course during several weeks, or
it ends in death within 10 days, preceded by coma and sometimes diarrhea. At
necropsy, liver, gall bladder and bile duct are distended and enlarged. White
nodules cover the surface of the liver. The protozoa can be found in the
liver and biliary ducts. An impression smear of the liver reveals the
presence of coccidia. Secondary infection can lead to their
presence in the nervous system. The disease is often accompanied by secondary
bacterial infection, in particular by Escherichia coli.
Diagnosis
Coccidiosis is very difficult to diagnose. It can be
done by fecal flotation, by identifying the oocysts in the feces, or under
the microscope by counting the coccidia per gram of
feces. Coccidian oocytes may be difficult to differentiate from the
rabbit-specific yeast, Cyniclomyces guttulatus. If tests
confirm the presence of E. intestinalis, E. flavescens, E.
irresidua and E. piriformis, treatment
should start immediately Treatment
Treatment
of hepatic coccidiosis is difficult and the disease may remain present for
life. The anti-coccidiosis treatment is successful only for rabbits infected
since 5 to 6 days. Even if the treatment is successful, mortality and
diarrhea will continue during the next few days. Relapse is regularly
observed after 1 or 2 weeks. Robenidine hydrochloride is well tolerated by rabbits, but its
regular preventive use over the last 20 years has raised resistance of e.g. E. media and E. magna toward
this compound. Further drugs used to treat the parasite include: Sulfonamide
and trimethoprim antibiotics have proven efficacious in the treatment of
coccidiosis. They should only be used to cure the disease, never as a
preventive measure. The most effective drug is sulphadimethoxine
(0.5 to 0.7 g / liter water). It is the well tolerated by pregnant and
nursing does. Other sulpha drugs include: ·
sulphaquinoxaline in drinking water: 1 g/litre; ·
sulphadimerazine in drinking water: 2 g/litre. ·
Salinomycine
(Bio-Cox®); ·
Diclazuril (Clinicox®); ·
Toltrazuril (Baycox®), 2.5
to 5 mg/kg (higher doses cause anorexia and decrease in size of fecal
droppings), twice, repeat after 5 days. Treatment
is best administrated to all the rabbits during a minimum of 5 days. The
treatment should be repeated after 5 days. Treatment of the environment
is important (e.g. 10% ammonia). Water crocks and feed hoppers should be
disinfected and remain free of rabbit feces. When treating a carpet, vacuum first in order to
further penetration of the anticoccidial product. During treatment of the
environment, rabbits should be kept in another part of the home to avoid the
danger of contact with the products and possible intoxication. Prevention
Branches
and leaves rich in tannin (willow, hazelnut, oak, ash, fruit trees,
eventually pines) are excellent in preventing coccidiosis. Before a rabbit is
given a twig to chew, it is important to check that it’s picked from a tree
that is not toxic to rabbits. Furthermore, the tree must not have been
exposed to chemicals or pollution from busy roads. Acknowledgements
All my gratitude to Prof. Richard Hoop (Institut für
Veterinärbakteriologie, University of Zurich), Dr K. Hermans (Kliniek voor
Pluimvee en Bijzondere Dieren, University of Gent, Belgium), to Michel Gruaz
(Switzerland) for the permission to use their pictures related to coccidiosis
in rabbits. Further Information
Arafa MA, Wanas MQ. The efficacy of ivermectin in treating rabbits
experimentally infected with Eimeria as indicated parasitologically and
histologically. J Egypt Soc Parasitol. 1996; 26(3):773-80. Atta AH, el-Zeni, Samia A. Tissue residues of some
sulphonamides in normal and Eimeria stiedai infected rabbits. Dtsch
Tierarztl Wochenschr. 1999; 106(7):295-8. Cere N, Humbert JF, Licois D, Corvione M,
Afanassieff M, Chanteloup N. A new approach for the identification and the
diagnosis of Eimeria media parasite of the rabbit. Exp Parasitol.
1996; 82(2):132-8. Coudert P., Licois D., Drouet-Viard F., Provôt
F. 2000. "Coccidiosis". In: Rosell
J.M. (ed), (Enfermedades del conejo), vol.II, chapter XVI, pp
219-234, Mundi-Prensa Libros,
Madrid, Spain. Licois D, Coudert P, Bahagia
S, Rossi GL. Endogenous development of Eimeria
intestinalis in rabbits. J Parasitol. 1992;
78(6):1041-8. Manger BR, 1991a Anticoccidials. In: Veterinary
Applied Pharmacology & Therapeutics (GC Brander, DM Pugh, RJ Baywater
& WL Jenkins, eds) Baillière Tindall, London (UK); pp 549-552, 1991 Pakandl M, Drouet-Viard F, Coudert P. How do
sporozoites of rabbit Eimeria species reach their target cells? C R
Acad Sci III. 1995; 318(12):1213-7. Pakandl M, Licois D, Coudert P. Electron microscopic
study on sporocysts and sporozoites of parental strains and precocious lines
of rabbit coccidia Eimeria intestinalis, E. media and E.
magna. Parasitol Res. 2001; 87(1):63-6. Peeters JE, Geeroms R. Efficacy of toltrazuril
against intestinal and hepatic coccidiosis in rabbits. Vet Parasitol. 1986;
22(1-2):21-35. Renaux S, Drouet-Viard F, Chanteloup NK, Le Vern Y,
Kerboeuf D, Pakandl M, Coudert P. Tissues and cells involved in the invasion
of the rabbit intestinal tract by sporozoites of Eimeria coecicola. Parasitol Res.
2001; 87(2):98-106. Rommel M, Eckert J & Kutzer E, Parasitosen des
Kaninchens. In: Veterinärmedizinische Parasitologie (J Eckert, E Kutzer, M
Rommel, HJ Bürger & W Körting, eds), Paul Parey Verlag, Berlin (D); pp
646-662, 1992 Vanparijs O, Hermans L, van der Flaes L, Marsboom R.
Efficacy of diclazuril in the prevention and cure of intestinal and hepatic
coccidiosis in rabbits. Vet Parasitol.
1989; 32(2-3):109-17. |
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