Chronic small intestinal diseases

Parasitic enteritis

Infestation with roundworms does occur especially in puppies and kittens. Where there is a heavy infestation in a puppy or kitten this may be associated with poor growth, distention of the abdomen and mucoid diarrhoea. They are rarely implicated in causing chronic diarrhoea in adult dogs and cats. The authors have examined faeces from many hundreds of dogs and cats as part of the investigation for chronic diarrhoea but detected roundworms in less than 5% of cases. Migrating larvae may cause damage to the lungs and liver especially if present in large numbers.

Hookworm infestation in the UK usually involves Uncinaria spp. which are not blood-sucking like Ancylostoma spp. Both may be implicated in causing diarrhoea if present in large numbers, with associated colic and melaena. In addition to these signs if the damage caused to the mucosa is severe, then plasma proteins may be lost into the intestine. Tapeworms even when present in large numbers rarely cause diarrhoea.

Diagnosis of roundworm infestation is made from examination of the faeces for ova. Where evidence of worms is detected, they should be treated and the animal reassessed at a later date, so that parasites can be definitively ruled out of the investigation into chronic diarrhoea.

Parasitic enteritis: Treatment

Treatment involves the use of an effective anthelmintic such as fenbendazole (Panacur; Hoechst Animal Health) 20mg/kg for 5 days or 100 mg as a single dose (Table Some anthelminthics suitable for the dog and cat). It is more important to ensure the dog and cat population is kept free of worms and this involves regular worming whether evidence of worms is present or not. This is especially true in the case of breeding bitches.

Table Some anthelminthics suitable for the dog and cat

Telmin KH Mebendazole Dog/cat 1 x 100 mg bid for 2 days adults½ x 100 mg bid for 2 days neonate
Panacur 10% Fenbendazole Dog/cat 20mg/kg for 5 days, or 100 mg as single dose
Fiperazine Piperazine Dog/cat 500mg/kg once
Strongid Paste Pyrantel Dogs 9 cm paste/4½ kg
Lopatol 100 Nitroscante Cats 1 x 100mg/4.4 kg
Lopatol 500 Nitroscante Dogs 1 x 500mg/22 lbs


Giardiasis in dogs and cats is now recognized to be more important than previously considered. Ingested cysts are the main source of infection, following faecal contamination of food. Giardia is not host specific so canine and feline infection can affect man (). In a UK survey Giardia cysts were detected in 13.9% of stray dogs’ faeces, all of which were carrying the parasite without clinical signs (). The prepatent period following ingestion appears at 4 to 8 days.

The trophozoites attach by means of a sucker to the duodenal mucosa and are therefore rarely observed in the faeces. Giardia rarely establishes below the jejunum. Problems occur most frequently in puppies and kittens where large numbers of Giardia are present and may alter the gut flora and induce changes to the brush border which lead to chronic diarrhoea and malabsorption.

Clinical diagnosis

Although asymptomatic carriers do exist many dogs and cats will exhibit signs which include the passage of soft, pale and unformed faeces which may appear granular or ‘frothy’ in appearance. Sometimes faeces are observed to be shiny or greasy due to steatorrhoea. Although individual episodes of diarrhoea may appear acute, there is usually a history of chronic or persistent diarrhoea.

Diagnosis is based on the examination of faeces for the presence of cysts. This must be carried out carefully as many methods are simply unreliable. Direct examination of the faeces may reveal trophozoites but they are often absent. A peroral method of sampling the duodenal juice has been shown to be very reliable (). Otherwise an ether extraction method which concentrates the cysts found in faeces should be employed ().

Giardiasis: Treatment

Once a diagnosis has been made, the animal should be treated with inetronidazole (Flagyl; RMB Animal Health) at 25mg/kg bid for 10 days. The faeces should be checked after the course of treatment to ensure that Giardia spp. has been eliminated. It is also advisable to inform the owner that Giardia is a zoonosis, and that strict hygiene is required during the treatment period.


Cryptosporidia spp. has been associated with enteritis in calves and other farm livestock but is very rare in small animals. A recent survey of stray dogs failed to find any evidence of the organism in faecal samples (). The condition has been reported more in the cat than the dog, especially where the cat is immunosuppressed ().

Clinical signs are those of fluid faeces and dehydration and are especially severe in kittens. Fortunately the condition is usually self-limiting. The organism is most often found in situations of poor hygiene and overstocking. Diagnosis is difficult to obtain and involves the careful examination of faeces for oocysts. Faecal flotation using Sheather’s sugar solution or acid fast stains has been employed.

Treatment involves the use of oral sulphonamides at 50 mg/kg/day for at least 10 days.

Lymphocytic-plasmacytic enteritis

Eosinophilic enteritis

Gluten sensitive enteropathy

The terms ‘sprue’ and ‘coeliac disease’ have been used to describe a similar condition seen in man. The condition recognized in the dog is due to a product of gluten digestion which is toxic to mucosal cells and elicits an immune response. Crypt mitosis is depressed and so epithelial renewal is reduced resulting in villus atrophy (). Familial sensitivity to gluten has been detected in the Irish Setter and appears to have a hereditary basis. It involves young dogs up to 1 year-old, where partial villus atrophy and malabsorption have been detected. The condition appears to be corrected when the dogs are placed on a gluten-free diet but relapses when a gluten diet is reintroduced. Biochemical studies of the brush border have shown a deficiency in aminopeptidase N which will result in a reduced degradation of gluten, leading to hypersensitivity. Increased intestinal permeability has also been detected (). Only puppies fed cereal-based diets were observed to have histological and biochemical changes to the small intestine. These included partial villus atrophy, lymphocyte infiltration, reduced levels of alkaline phosphatase and aminopeptidase N, and finally increased permeability ().

Clinical diagnosis

The condition should be suspected in young Irish Setters which exhibit signs of weight-loss or failure to thrive in association with chronic intermittent diarrhoea. They are often between 4 and 7 months of age. Diagnosis is further confirmed by low serum folate levels but normal B12 levels suggesting a proximal small intestinal malabsorption. There is often reduced xylose absorption. A definitive diagnosis is made from biopsy of the duodenum and jejunum where partial villus atrophy, lymphocyte infiltration and loss of brush border enzymes are detected.

Gluten sensitive enteropathy: Treatment

Affected dogs should be placed on a gluten-free diet and maintained on this once symptoms have disappeared. This means the diet must be free of cereal products and when such a diet is instigated the histological changes in the small intestine slowly reverse and clinical signs disappear. Rice-based foods and tinned meat should be used rather than cereals such as wheat and maize. A low fat diet is also helpful and a good vitamin mineral supplement should also be provided. In severe cases prednisolone and tylosin should be given in a similar manner to that used in lymphocytic—plasmacytic enteritis.

Regional enteritis

Regional enteritis is also known as granulomatous enteritis and Crohns disease in man. Although recorded in the dog () and the cat () it is rare compared with the number of cases seen in man. The aetiology for this inflammatory condition of the intestine is not known although it has been associated with Trichuris larvae (). Male dogs appear most frequently involved especially those under 4 years of age. The condition is progressive and involves the ileum and possibly the caecum and colon. Segments of affected intestine lie next to segments of normal intestine. There appears to be some association between regional enteritis and perianal fistulas in some dogs.

Clinical diagnosis

Both dogs and cats present with diarrhoea often containing fresh blood and mucus. Faeces are small in volume and tenesmus is often present, especially where the terminal colon is involved. Occasionally patients will vomit and exhibit abdominal pain. Weight-loss is a feature especially in advanced cases and in all cases the signs may wax and wane.

Laboratory investigation may reveal an eosinophilia, and hypoproteinaemia in advanced cases. The only method of obtaining a definitive diagnosis is the biopsy of affected sections of intestine and lymphoid tissue at laparotomy. Histologically there is involvement of all layers which are thickened and contain cellular infiltrates. Large numbers of eosinophils, plasma cells, lymphocytes, multinucleate giant cells and macrophages are seen. The regional lymph nodes are similarly affected.

Regional enteritis: Treatment

The use of corticosteroids, azathioprine and tylosin have all been advocated at closes similar to those for lymphocytic—plasmacytic enteritis. Surgical resection of affected intestine has also been carried out in cases where the changes are not extensive. In all reported cases the outcome has been death or euthanasia, therefore the prognosis must be considered very guarded indeed.


Intestinal neoplasia

Around 60°<> of intestinal tumours occur in the small intestine (). They include lymphosarcoma, adcnocarcinoma, adenoma, leiomyosarcomas. Lymphosarcoma is the commonest tumour observed in dogs and cats followed by adenocarcinoma (). Tumours may result in malabsorption, obstruction, bacterial overgrowth or protein-losing enteropathy. Lymphosarcoma is seen mainly in young animals while adenocarcinomas is seen in the middle to old-age group.

Lymphosarcomas may cause malabsorption and protein-losing enteropathy, but rarely cause intestinal obstruction because of the intraluminal nature of their growth. Clinically the dog or cat exhibits chronic intermittent diarrhoea with a slow onset of weight-loss and variable appetite. Cats suspected of this condition should be examined for FcLV, as up to 30% may be positive. Diagnosis is based on signs of hypoproteinaemia including subcutaneous oedema, ascites and hydrothorax, and detecting malabsorption from reduced xylose and fat absorption. Biopsy of the small intestine especially the ileum will reveal grossly thickened intestinal walls and generalized lymphocyte infiltration which includes the mesemeric lymph nodes (). The prognosis is poor in all cases, but chemotherapy can be attempted using vincristine (Oncuvin; Eli Lilly & Co.), cytosine arabinosidc (Cytosar; Upjohn), cyclophosphamide (Endoxana; Boehnnger Ingelheim) and prednisolone in combination. This regime has been adopted lor treatment of multicentric lymphosarcoma and leukaemias but there are no reports of successful use of this treatment in intestinal lymphosarcoma.

Adenocarcinoma is seen most frequently in the duodenum and large intestine. Siamese cats and generally those over 11 years appear to be most frequently affected. There is proliferation of a segment of the intestine which grows into the lumen causing signs of obstruction (). Alucosal ulceration develops leading to the presence of observable amounts of blood in the faeces. Other clinical signs may include vomiting and anorexia. The condition is one of slow insidious onset with an acute terminal phase. Often the tumour is well-advanced at the time of diagnosis and may involve other loops of intestine, adhesions or metastasis to other tissues. Radiographs are often helpful in making a diagnosis. The prognosis must be very guarded, but if there are no signs of spread then surgical excision can be successfully carried out.


Selections from the book: “Digestive Disease in the Dog and Cat” (1991)