Protozoal enteritis: Coccidiosis
Esther van
Praag, Ph.D.
Warning: this page contains pictures that may be distressing for some persons.
|
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 stimulate 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 oocysts. 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 immunosupression. 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. The eggs of coccidia are often 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 / liter; ·
sulphadimerazine in drinking water: 2 g / liter. ·
Salinomycine
(Bio-Cox®); ·
Diclazuril (Clinicox®); ·
Toltrazuril (Baycox®), 2.5
to 5 mg/kg (higher doses cause anorexia), 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
My gratitude goes 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. |
||||||||||||||
e-mail: info@medirabbit.com
