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Infectious Diseases of Rabbits

Authors:
  • College of Veterinary and Animal Sciences Udgir Maharashtra India

Abstract

Nowadays rabbit farming is among one of the fastest growing industry. The use of rabbits for meat, fur, as a pet animal and as laboratory animal for various experimental trials increased demand of rabbits in market. So, rabbit breeders and pet owners should have idea about important diseases of rabbits to avoid economic loss, zoonotic threat & to provide disease free animal model for various research trails. So, in present article we discussed various economically important infectious diseases of rabbits according to causative agents.
1
Infectious Diseases of Rabbits
Chavhan S G
4
, Babu Lal Jangir
1
, Kurkure N V
2
and Chopade N A
3
1. PhD Scholar, Indian Veterinary Research Institute, Izatnagar, Bareilly, Uttar Pradesh- 243122
2. Associate Professor, 3. Senior Research Fellow, Dept. of Vety. Pathology, Nagpur Veterinary College, MAFSU, Nagpur, Maharashtra-
440006
4. Corresponding Author: Dr. Sambhaji G. Chavhan, Assistant Professor, Department of Veterinary Pathology, Veterinary College,
KVAFSU, Bidar, Karnataka-585401
Email: drsam24183@gmail.com Website: www.vetclinpath.in
INTRODUCTION
Nowadays rabbit farming is among one of the fastest growing industry. The use of rabbits for
meat, fur, as a pet animal and as laboratory animal for various experimental trials increased
demand of rabbits in market. So, rabbit breeders and pet owners should have idea about
important diseases of rabbits to avoid economic loss, zoonotic threat & to provide disease
free animal model for various research trails. So, in present article we discussed various
economically important infectious diseases of rabbits according to causative agents.
[A] BACTERIAL DISEASES
1. Pasteurellosis:
Pasteurellosis in rabbits is caused by Pasteurella multocida. Transmission occurs by direct
contact, aerosol, venereal, and hematogenous routes. Upper respiratory disease (snuffles),
pneumonia, otitis media, pyometra, orchitis, subcutaneous abscesses, conjunctivitis and
septicemia are manifestations of P. multocida infection in rabbits.
a) Snuffles: This is the most common manifestation of pasteurellosis. Clinical signs
characteristically include serous to mucopurulent nasal exudates with sneezing and
coughing. Exudates may be seen on the medial aspect of the forepaws. Signs may subside
temporarily only to recur throughout life. Lesions include reddened mucosa in acute
infections, thickened mucosa in chronic infections and exudates in nasal cavity and paranasal
sinuses.
b) Enzootic Pneumonia: Affected rabbits frequently die acutely with no signs (especially
young rabbits); anorexia and depression may be observed. Acute pneumonia lesions include
red grey foci of consolidation of the cranio-ventral lung lobes with or without hemorrhage.
Chronic pneumonia is characterized by generalized consolidation, encapsulated abscesses and
fibrino-purulent lesions.
c) Otitis media: Torticollis occurs if the function of the internal ear is compromised, either
by direct bacterial invasion or by the damaging effects of the bacterial toxins. Nervous signs
and incoordination are observed if the bacteria extend to the meninges. Creamy white
exudates in middle ear is found either uni- or bilaterally.
d) Genital infections: Venereal or hematogenous transmission may occur. Affected rabbits
may have a vaginal discharge which may be serous to mucopurulent and/or a history of
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infertility. The uterus can be palpably enlarged with pyometra. Acute infection of the uterus
is characterized by slightly dilated horns filled with grey exudate. In chronic infections the
uterine horns are greatly dilated with purulent exudate, and are fragile. In affected bucks, one
or both testicles may be enlarged, tender, firm and may contain abscesses.
2. Bordetellosis:
Bordetellosis is caused by Bordetella bronchiseptica is a small Gram negative, alpha-
hemolytic, non-fermenting rod. Routes of transmission include aerosol and direct contact.
Clinical signs are similar to snuffles and include upper respiratory infection with serous to
mucopurulent nasal exudate and sneezing. Pneumonia uncommonly develops. The
characteristic lesion is erythematous nasal mucosa with adherent exudates.
3. Colibacillosis:
Colibacillosis is caused by Escherichia coli is a Gram negative, lactose-fermenting, indole
positive rod. Rabbits are known to be affected by non-toxin producing, enteropathogenic E.
coli. Rabbits have diarrhea, fever, anorexia and may consume more water than usual. Fecal
stained perineal fur and fluid-filled intestinal contents with serosal vascular injection are
seen.
4. Tyzzer's Disease:
Clostridium piliforme causes Tyzzer’s disease in rabbits. The disease is spread by spore
ingestion. The disease is perpetuated in breeding colonies by the infection of bunnies born
into the colony. Usually rabbits are found affected shortly after weaning after lapse of
passive immunity. Acute, profuse watery to mucoid diarrhea, dehydration and death within
12 to 48 hours after onset of diarrhea are typical. The mortality rate is high. Lesions in
weanling rabbits include edema and hemorrhage of mucosa, submucosa, and musculature of
intestinal tract. It is unusual to see an enlarged liver with multifocal tan to yellow foci of
necrosis or hemorrhage of the myocardium. Extensive mucosal necrosis with a
granulomatous cellular mucosal infiltrate may occur in the ileum, cecum, and proximal colon.
Visualization of the bacterium is enhanced with use of silver stains. Argyrophilic intracellular
bacteria in clusters or "pick-up-sticks" or haystack clumps are present in viable enterocytes in
areas of granulomatous enteritis and if hepatic necrosis is observed, in hepatocytes adjacent
to an area of necrosis.
5. Staphylococcus infections:
Staphylococcus infections are caused by Staphylococcus aureus. Aerosol and direct contact
(organism present in oral cavity of non-clinical carriers) are primary routes of infection.
There is a wide range of clinical disease forms. S. aureus may cause suppurative infection in
any organ or any site. Subcutaneous abscesses, mastitis with abscess formation, dermatitis,
upper respiratory infection with mucopurulent nasal discharge, and septicemia with
depression, anorexia, fever, and deaths have been reported. Of these disease syndromes,
abscess formation and mastitis are most commonly reported.
Mastitis: Mastitis or blue breast disease is commonly found in herds with intensified
production. Infection of gland occurs through trauma to the teat, ascending infection through
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the teat canal or secondary to septicemia. Mastitis occurs just after kindling. The mammary
glands are swollen, usually not discolored and may develop abscesses. Frequently there is
loss of function of the affected gland and rarely the doe may die. Bunnies may die because of
infected milk or not grow as well because of decreased function of the gland.
6. Venereal Spirochetosis:
Treponema paraluis cuniculi is a spiral-shaped bacterium related to the human syphilis
organism, Treponema pallidum is causative agent of venereal spirochetosis. It is also known
as Rabbit Syphilis, Vent Disease, and Cuniculosis. Genital transmission is most common.
Erythema of mucous membrane of external genitalia that progresses to focal, raised, crusty
ulcerations is the most common sign. Lesions can occur on the perineal area and face due to
auto-inoculation. As ulcerations heal, a dry scaly condition follows. Spontaneous regression
usually occurs in several weeks. The bacteria cause only superficial, cutaneous pathology.
There may be popliteal and inguinal lymph node enlargement. Mild or subclinical disease is
common. Reluctance to breed and decreased reproductive efficiency may occur.
7. Proliferative Ileotyphlitis:
Chronic diarrhea with wasting and proliferative enteritis in rabbits has been associated with
infection with a Lawsonia-like organism. The bacterium can be demonstrated within ileal or
cecal enterocytes by use of silver chemical stains or amplified by a Lawsonia-specific PCR
assay. There is little known about the disease pathogenesis, but the etiologic agent (and the
resultant disease) is similar to that of proliferative enteritis of swine. Concurrent diseases or
stressors seem to be associated with development of the proliferative enteric lesion with
intracellular bacteria. Oral administration of kaolin may be helpful when this infection is
suspected.
8. Salmonellosis:
Salmonella enterica serovars are responsible for Salmonellosis in rabbits. Salmonellae are
transmitted by ingestion through direct contact with contaminated feces, food or fomites.
Incidence of infection is rare. Acute disease is characterized by anorexia, fever, dehydration,
diarrhea (hemorrhagic), death and abortions. Rabbits that recover from acute disease are
asymptomatic shedders. Lesions are consistent with those of septicemia and include
congestion and hemorrhage of the viscera associated with septicemia, ulcerative colitis and
focal necrosis of liver.
9. Tularemia:
Francisella tularensis causes tularemia. Blood sucking arthropods (squirrel flea, deerfly,
mosquitoes, lice and wood ticks) may serve as mechanical or biological vectors.
Transmission may occur by direct contact, ingestion, or aerosol. Depression, anorexia, ataxia
and death are the nonspecific signs associated with this disease. Widespread visceral
congestion, splenomegaly, consolidated and congested lungs and multiple pinpoint white foci
on the liver and spleen are characteristic lesions.
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[B] VIRAL DISEASES
1. Myxomatosis:
Myxomatosis is caused by any one of several strains of myxoma virus, a member of the
leporipoxvirus group. The principal mode of transmission is via arthropod vectors
(mosquitoes, fleas, flies, gnats). Transmission may also occur by contact with infected
material from ocular discharges or oozing skin lesions of infected rabbits, contaminated
spines of thistles and the claws of predatory birds. Virus-infected skin nodules on wild
rabbits, Syvilagus sp., are reservoirs of the agent. The most prominent gross lesions are skin
tumors and pronounced cutaneous and subcutaneous edema. Skin hemorrhages and
subserosal petechial and ecchymotic hemorrhages in the stomach and intestines may be
observed.
2. Viral Hemorrhagic Disease:
The disease was first reported in China in 1984 and has since been reported in Europe, parts
of Asia, Mexico and the United States. It is also known by different names Viral hemorrhagic
fever, viral necrotizing hepatitis. A calicivirus has been recovered from infected rabbits.
Apparently strains of virus with varying degrees of virulence have been recovered from
rabbits from different parts of the world. The agent can be spread by direct contact, biting
arthropods and fomites, including handling of infected rabbit meat and by products. The
incubation period ranges from 1 to 3 days, at which time one of three forms of the disease
may be seen.
The peracute disease is manifested by death without clinical signs. In acute disease,
acute onset of anorexia and lethargy occur followed by labored respiration. Body
temperature may be elevated from 40 to 41
o
C, but rapidly declines prior to death. In subacute
disease, clinical disease progresses to include bloody nasal discharge, opisthotonus and
vocalization. Death occurs 2 to 3 hours after the onset of clinical signs. In colony settings,
morbidity may reach 90% with 100% mortality. Tracheal hemorrhages, petechia on the
myocardium, kidney and spleen, pulmonary edema and congestion and widespread hepatic
necrosis are frequently observed at necropsy.
3. Oral Papillomatosis:
A member of the papovavirus group causes oral papillomatosis, rabbit oral papilloma virus.
Spread is by direct contact of oral secretions containing sloughed epithelial cells from the oral
warts. Infection occurs in the abraded epithelium of the tongue. This is a benign disease
characterized by numerous whitish growths on the underside of the tongue, oral cavity
epithelium or gingiva. These later become pedunculated and ultimately ulcerate. The
growths regress when the rabbit becomes immune. A typical papilloma with verrucous
epidermal hyperplasia with rete peg formation and hyperkeratosis and dermal fibroplasia has
been described. Intraepithelial viral inclusion bodies are not usually seen on microscopic
examination of tumors.
4. Rabbit (Shope) Fibroma Virus:
Fibroma virus is a member of the leporipoxvirus group and is closely related to myxoma
virus. The natural transmission cycle is not known although arthropod vector transmission is
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likely. Tumors occur on the legs or feet, on the muzzle, and around the eyes. The tumors are
subcutaneous and not attached to underlying tissue. Metastases from the original tumor do
not occur. The infected adult rabbit remains clinically normal otherwise. Tumors will
typically regress after a period of months.
5. Rabbit (Shope) Papilloma Virus:
A member of the papovavirus group is causative agent. This disease is seen most frequently
in cottontail rabbits of the Midwest with outbreaks in domestic rabbits. Arthropod vector
transmission of the natural disease has been demonstrated. The mosquito is thought to be the
main vector in transmission from feral to domestic rabbits. Horny warts are found on the
eyelids and ears. The growths are well keratinized, and the upper surface is irregular and
split. The growths are easily scratched or knocked off. These sites later heal without
complication.
[C] PARASITIC DISEASES
1. Diseases Caused by Nematodes:
i) Baylisascaris procyonis: Infection of rabbits with the raccoon ascarid, Baylisascaris
procyonis, occurs by ingestion of bedding or hay contaminated with raccoon feces. Clinically
infected rabbits display torticollis, ataxia, tremors, and falling (loss of balance). At necropsy,
multiple, white raised nodules in the epicardium, endocardium and serosal surface of the liver
may be seen. Larval granulomas and multifocal necrosis in the cerebrum and cerebellum,
and larval granulomas and tracks in the viscera are typical microscopic lesions. Cross
sections of larvae with cuticular alae are often visualized in brain sections.
ii) Passalurus ambiguus
The rabbit pinworm does not cause clinical disease in infected rabbits. The rabbit pinworm
has a direct life cycle and adult pinworms reside in the cecum and large intestine.
2. Diseases Caused by Cestodes:
Wild rabbits are definitive and intermediate hosts for a number of tapeworms. The life
cycles of these parasites practically precludes infection of domestic or laboratory rabbits.
Taenia pisiformis infections are very common in wild rabbits and are found occasionally in
domestic rabbits. The stage found in rabbits is a cysticercus. Most cysticerci are found in the
liver or attached to the mesentery and cause little damage. A second taenid found in rabbits
is T. serialis. The stage of the cestode seen in rabbits is a coenurus, which occurs in
connective tissue of muscle. Infection in wild rabbits is less common than T. pisiformis and
is extremely rare in domestic rabbits. The dog is the definitive host of both cestodes.
3. Diseases caused by Protozoa:
i) Coccidiosis:
(a) Hepatic Coccidiosis: Hepatic Coccidiosis is caused by Eimeria stiedae. Ingestion of
sporulated oocysts (unsporulated in freshly voided feces) is the mode of transmission. The
incidence of infection is moderate to high. Signs predominate in young rabbits and may
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include anorexia, debilitation, and pendulous abdomen with hepatomegaly noted on
abdominal palpation. Mortality is low except in young rabbits.
An enlarged liver with multifocal, flat, yellow-white lesions containing yellow
exudate and occasionally a distended gallbladder that contains bile may be seen at necropsy.
The pathognomonic microscopic lesion is marked periportal fibrosis surrounding enlarged
bile ducts lined with hyperplastic bile duct epithelium that harbors inflammatory cell
infiltrates and E. stiedae macrogametes, microgametocytes and oocysts.
b) Intestinal coccidiosis:
Eimeria magna, Eimeria irresidua, Eimeria perforans and Eimeria media are frequently
observed pathogenic species. All species infect the intestinal tract and replicate in the
absorptive epithelium of the mucosa. Transmission occurs by ingestion of sporulated
oocysts. Signs vary and are most severe in young rabbits. Poor weight gain, diarrhea
ranging from mucoid to watery to hemorrhagic, polydipsia and sometimes acute death are
seen. Older rabbits may shed coccidial oocysts without expression of clinical disease. Fluid
intestinal contents are often observed in heavily parasitized rabbits. One may see multiple
white patches or ulcers on mucosal surface of the small or large intestine.
ii) Encephalitozoonosis:
Encephalitozoon cuniculi (Nosema cuniculi) is a microsporidian parasite, which causes
Encephalitozoonosis. E. cuniculi is shed in the urine and has been experimentally transmitted
by direct contact (ingestion, aerosol). Usually there are no clinical signs (latent infection);
however, in heavy infections there may be torticollis, convulsions, tremors, posterior paresis,
and edema. In acute cases the kidneys are swollen. Chronic lesions are more commonly seen
and include multifocal, pinpoint, white, pitted areas on the surface of the kidneys.
Histological examination of kidneys and brain will reveal a granulomatous interstitial
reaction with fibrosis in the kidney and focal granulomas in the brain (white arrow) with
perivascular plasma cell cuffs and non-suppurative meningitis.
4. Diseases Caused by Mites:
i) Psoroptes cuniculi (ear mite): This non-burrowing, obligate mite has a high incidence of
occurrence in meat, laboratory and pet rabbits. Scratching at ears with hind feet and the
presence of crusty exudate in the pinnas with an underlying moist dermatitis are
characteristic. The parasites do not cause otitis media since they do not penetrate the
tympanic membrane.
ii) Cheyletiella parasitovorax (fur mite): C. parasitovorax is a small, noninvasive mite, with
a low to moderate incidence of infection. Partial alopecia of dorsal trunk or scapular region
with a fine, grey scale on erythematous skin results from infestation. (The mite is often
called "walking dandruff").
iii) Listrophorus gibbus (fur mite): L. gibbus is a small, non-burrowing might present at low
to moderate incidence in domestic rabbits. It is an obligate parasite, completing all stages of
the life cycle on the host. This mite is currently considered non-pathogenic and is found
primarily on the back and abdomen.
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5. Diseases Caused by Flies, Fleas and Lice:
i) Cuterebrid flies infection:
Cuterebrid flies are also known as rodent and rabbit warble flies. Cuterebriasis occurs most
frequently in wild rabbits, but may occur in domestic rabbits housed outdoors. Incidence
peaks in the summer and late fall. Single or multiple large subcutaneous swellings containing
encysted larvae with a fistula in the center are the characteristic lesions. When the larval fly
is ready to pupate, it leaves the swelling and drops to the ground.
ii) Ctenocephalides infection:
Rabbits are commonly infested with Ctenocephalides sp., especially C. felis. The infestation
may be asymptomatic, but may induce mild pruritis and alopecia.
iii) Haemodipsus ventricosis (Blood sucking louse):
The anapleurid louse is rarely found on domestic rabbits. Weakness, anemia, ruffled fur and
pruritis (secondary dermatitis) are common signs of infection.
[D] DISEASES CAUSED BY FUNGI
Trichophyton mentagrophytes is an opportunistic, ubiquitous fungal soil organism. There is
high incidence of the carrier state, with low incidence of disease. A crusty, pruritic, patchy
alopecia on the head that spreads to the paws and other parts of the body is typical. Secondary
bacterial infections are common.
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Harkness JE, Turner PV, Woude SV and Wheler CL. 2010. Specific Diseases & Conditions
of Rabbits & Rodents. In: Harkness & Wagner’s The Biology and Medicine of Rabbits
and Rodents. 5
th
Edn., Blackwell Publishing, Ames, Iowa, USA. pp: 249-394.
Hillyer EV and Quesenberry KE. 1997. Disease Problems of Guinea Pigs & Chinchillas. In:
Ferrets, Rabbits and Rodents: Clinical Medicine and Surgery, 1
st
Edn, W. B. Saunders
Company, Philadelphia, USA. pp: 260-282.
Maertens L and Coudert P. 2006. Rabbit Hemorrhagic Disease. In: Recent Advances in
Rabbit Sciences. 1
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Edn., Institute of Agricultural and Fisheries Research (ILVO),
Belgium. pp: 187- 197.
Manning PJ, Ringler DH and Newcomer CE. 1994. Bacterial and Viral Diseases. In: The
Biology of the Laboratory Rabbit. 2
nd
Edn., Academic Press Limited, London, UK. pp:
131-230.
Percy DE and Barthold SW. 2007. Rabbit Diseases. In: Pathology of Laboratory Rodents and
Rabbits. 3
rd
Edn., Blackwell Publishing, Ames, Iowa, USA. pp: 253-307.
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... In general, rabbit farms are considered the fastest growing industry for their income, which is derived from meat, fur, or the use of rabbits as experimental animals for laboratory trials. Thus, it is crucial to determine important rabbit diseases to avoid economic loss and zoonotic threats [40]. For this reason, we focused on cases of aborted female does because reproductive females are the most important link in the production chain and recorded the bacterial pathogens present in different organs. ...
Article
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Background and aim: Rabbits are a highly sensitive species and susceptible to various bacterial pathogens that may be causative agents for early embryonic death. This study aimed to explore the administration of different bacterial agents in does suffering from early embryonic death. Furthermore, identification of genes associated with virulence was performed to identify the phenotypic and genotypic antimicrobial resistance patterns that may increase the virulence of pathogens and lead to early embryonic death. Materials and methods: We isolated and identified bacterial agents in 106 samples from live and dead female rabbits that had undergone early embryonic death, including liver and intestine tissue, aborted fetuses, discharges, and vaginal swabs. Conventional polymerase chain reaction (PCR) was conducted to confirm the identity of the isolated bacterial strains and their virulence. Moreover, antibiotic resistance was studied phenotypically and genotypically. Results: We isolated Escherichia coli, Salmonella, Staphylococcus aureus, Pasteurella multocida, and Listeria monocytogenes. PCR confirmed typical identification except in P. multocida, which was confirmed as Gallibacterium spp. in some cases. The final percentage of detection was 34%, 30.2%, 16.9%, 13.2%, and 11.3%, respectively. Virulence properties were investigated using different designated genes. All Salmonella strains harbored invA, stn, avrA, and ompf genes, while the sopE gene was identified in 31.25%. E. coli strains harboring the iss gene lacked the shiga toxin (stx1) gene. L. monocytogenes and S. aureus strains harbored the hemolysin gene (66.7% and 33.4%, respectively). Multidrug resistance was detected phenotypically and genotypically in most strains. Each bacterial pathogen had a different antibiotic resistance profile. Conclusion: Multiple bacterial species may contribute to early embryonic death in does. Furthermore, the combined infection could be the main cause of early embryonic death. Thus, monitoring programs should bear this in mind and focus on the early detection of these bacterial agents in female rabbits to avoid embryonic death.
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Rabbit hemorrhagic disease (RHD) is responsible for the deaths of millions of pet, commercial, and free-ranging rabbits worldwide. This article reviews the clinical signs, history, etiology, pathology, diagnosis, and control methods of RHD. The details surrounding the first outbreak of RHD in the United States and its implications are also explored.
Disease Problems of Guinea Pigs & Chinchillas. In: Ferrets, Rabbits and Rodents: Clinical Medicine and Surgery, 1 st Edn
  • E V Hillyer
  • K E Quesenberry
Hillyer EV and Quesenberry KE. 1997. Disease Problems of Guinea Pigs & Chinchillas. In: Ferrets, Rabbits and Rodents: Clinical Medicine and Surgery, 1 st Edn, W. B. Saunders Company, Philadelphia, USA. pp: 260-282.
Specific Diseases & Conditions of Rabbits & Rodents. In: Harkness & Wagner's The Biology and Medicine of Rabbits and Rodents. 5 th Edn
  • J E Harkness
  • P V Turner
  • Woude Sv
  • C L Wheler
Harkness JE, Turner PV, Woude SV and Wheler CL. 2010. Specific Diseases & Conditions of Rabbits & Rodents. In: Harkness & Wagner's The Biology and Medicine of Rabbits and Rodents. 5 th Edn., Blackwell Publishing, Ames, Iowa, USA. pp: 249-394.
Bacterial and Viral Diseases
  • P J Manning
  • Ringler Dh
  • C E Newcomer
Manning PJ, Ringler DH and Newcomer CE. 1994. Bacterial and Viral Diseases. In: The Biology of the Laboratory Rabbit. 2 nd Edn., Academic Press Limited, London, UK. pp: 131-230.
Rabbit Diseases. In: Pathology of Laboratory Rodents and Rabbits. 3 rd Edn
  • Percy De
  • S W Barthold
Percy DE and Barthold SW. 2007. Rabbit Diseases. In: Pathology of Laboratory Rodents and Rabbits. 3 rd Edn., Blackwell Publishing, Ames, Iowa, USA. pp: 253-307.
Ctenocephalides infection: Rabbits are commonly infested with Ctenocephalides sp., especially C. felis. The infestation may be asymptomatic, but may induce mild pruritis and alopecia
  • Ii
ii) Ctenocephalides infection: Rabbits are commonly infested with Ctenocephalides sp., especially C. felis. The infestation may be asymptomatic, but may induce mild pruritis and alopecia.