Malaysia is now in the Monsoon Season. This season is most feared by all farmers and breeders. During this season, the unpredictable strong wind and heavy rainfall can cause death. The drop in the temperature at night can also kill the younglings. And afar from that, there are also some diseases that attack the rabbit during the rainy season in Malaysia. Several gastrointestinal diseases are most common and how to prevent and cure them:
1. Colibacillosis (A diarrhea disease caused by Escherichia coli )
A. Etiology: Escherichia coli is a gram-negative, lactose-fermenting, indole positive rod. Rabbits are known to be affected by non-toxin producing, enteropathogenic E. coli (EPEC). EPEC adhere to the intestinal mucosa through a 2-step process. First, a bacterial pilus first allows attachment of the bacterial cell to the enterocyte. Second, a more intimate attachment through the eae pathogenicity island disrupts the cytoskeleton and destroys microvilli. A secretory diarrhea is induced by an unknown mechanism. Receptors for EPEC attachment to the epithelial cells are not present in newborn rabbits. They first appear at 21 days and reach normal adult levels by 35 days. The stress of weaning and loss of passively acquired maternal antibody contribute to susceptibility at this time.
B. Clinical Signs: Rabbits have diarrhea, fever, anorexia, and may consume more water than usual.
C. Pathology: Fecal-stained perineal fur and fluid-filled intestinal contents with serosal vascular injection are seen. Edema and pyogranulomatous cellularity of the lamina propria without mucosal ulceration are prominent histopathologic findings. Edema or hemorrhage can be seen in the submucosa. Small bacterial rods (arrow) adhered to and effacing enterocyte margins are common in the ileum and cecum.
D. Treatment: Fluid therapy and supportive care are indicated. The salicylates in Pepto bismol may be protective. Chlorpromazine (1 to 10 mg/kg IM) may help decrease fluid loss from the the secretory diarrhea.
2. Tyzzer's Disease
A. Etiology: Clostridium piliforme, an obligate intracellular bacterium, is a Gram-negative, pleomorphic, filamentous organism that can produce spores.
B. Transmission: The disease is spread by spore ingestion (fecal-oral). Spores can remain viable at moderate to freezing temperatures for extended periods of time (> 1 year). The disease is perpetuated in breeding colonies by the infection of bunnies born into the colony. The incidence of disease is moderate.
C. Clinical Signs: Usually rabbits are affected shortly after weaning when passive immunity, if present, has waned. 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. Exposure of naive adult rabbits may cause little to no clinical disease.
D. Pathology: Lesions in weanling rabbits include edema and hemorrhage of mucosa, submucosa, and musculature of intestinal tract (A.). It is unusual to see an enlarged liver with multifocal tan to yellow foci of necrosis or hemorrhage of the myocardium as is described in the literature. 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 (B.), and if heaptic necrosis is observed, in hepatocytes adjacent to an area of necrosis.
E. Diagnosis: Histopathological examination of liver or cecum stained with silver will be diagnostic if intracellular bacterial rods are observed. PCR of feces, intestinal tissue or liver can be used to document the presence of the bacterium. An ELISA is useful to detect antibody in recovered or asymptomatically infected rabbits.
F. Treatment: No therapy has been uniformly successful. Supportive therapy may help when the enteric disease is mild and the rabbit is still eating.
G. Control: Prevent overcrowding and use good sanitation techniques. Stresses such as weaning and high environmental temperature may precipitate an outbreak. To minimize the stress of weaning, let the bunnies stay in the original cage and remove the doe. Work to prevent temperature fluctuations and keep the rabbits well-ventilated in high temperatures with fans. The spores are resistant to many disinfectants. A 1% bleach solution will inactivate spores that remain after the fecal material has been washed off soiled cages. Temperatures of water used to clean cages may also inactivate spores if the cages and supplies are allowed to contact 180oF water for no less than 15 minutes.
3. Coccidiosis
A. Hepatic Coccidia
1. Etiology: Eimeria stiedae
2. Transmission: Ingestion of sporulated oocysts (unsporulated in freshly voided feces) is the mode of transmission. The incidence of infection is moderate to high.
3. Pathogenesis: Eimeria stiedae excysts in the duodenum, travels to the liver via the bloodstream or lymphatic, and invades epithelial cells of bile ducts to begin schizogeny.
4. Clinical Signs: Signs predominate in young rabbits and may include anorexia, debilitation, and pendulous abdomen with hepatomegaly noted on abdominal palpation. Mortality is low except in young rabbits.
5. Pathology: 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 (A.). 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.
7. Diagnosis: An antemortem diagnosis can be made by examination of feces by direct smear, flotation or concentration/flotation methods. It can be difficult to identify E. steidae oocysts in fecal specimens since they may not be readily shed in the bile. On necropsy, the recognition of the flat liver lesions and identification of oocysts in the bile provide diagnostic information. The histological appearance of liver with identification of intraepithelial coccidial organisms will allow diagnosis from tissue biopsies.
8. Treatment: Drugs approved as coccidiostats for rabbits used for meat in US include sulfamerazine (0.02% in water), sulfaquinoxaline (0.05% in water or 0.03% in feed), sulfamethoxine (75 mg/kg BW in feed), and lasalocid (68-113 gms per ton of feed). Hepatic coccidia are difficult to eliminate with anticoccidial therapy, and lasalocid has been the most successful of the listed drugs in treating hepatic coccidiosis.
9. Control: Rabbits should be housed on wire-meshed floors. Bottoms of cages are to be brushed daily to remove adherent feces, and cleaned and disinfected regularly (1% chlorox). Weanlings should be raised separate from adults. Feeding fresh greens or hay will prevent use of forage that may be contaminated with droppings from wild rabbits.
B. Intestinal Coccidia
1. Etiology: 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.
2. Transmission: Transmission occurs by ingestion of sporulated oocysts. Incidence of infection is high.
3. Clinical Signs: 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.
4. Gross Pathology: 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.
5. Diagnosis: Antemortem diagnosis can be made by examination of feces by direct smear, flotation or concentration/flotation methods. A postmortem diagnosis can be made on examination of mucosal scrapings and by observation of coccidial organisms on histological sections of intestine.
6. Treatment: As mentioned in the above section, drugs approved as coccidiostats for rabbits used for meat in US include sulfamerazine (0.02% in water), sulfaquinoxaline (0.05% in water or 0.03% in feed), sulfamethoxine (75 mg/kg BW in feed), and lasalocid (68-113 gms per ton of feed) have been provided in schedules of 3-weeks-on / 3-weeks-off periods.
7. Control: Rabbits should be housed on wire-meshed floors. Bottoms of cages are to be brushed daily to remove adherent feces, and cleaned and disinfected regularly (1% chlorox). Weanlings should be raised separately from adults. Feeding fresh greens or hay will prevent use of forage that may be contaminated with droppings from wild rabbits.
Taken from: All About Animals
