Esophagus and Stomach
Spirocerca lupi is the main parasite that infects the esophagus and stomach in dogs. S. lupi is a nematode usually found in the esophageal wall, more rarely in the stomach or even in the wall of the aorta. These parasites cause a serious disease that is endemic in tropical countries, northern Africa, and southern Europe. Dogs become infested by ingesting intermediate hosts, usually Coleoptera (beetles), or more commonly, small vertebrates.
Diseased animals show symptoms in the esophagus (regurgitation, sometimes inability to swallow) and stomach (repeated vomiting, increased thirst). Respiratory difficulties may be observed when the parasite is located in the wall of the aorta. Treatment is very difficult, involving injectable anthelminthics such as ivermectin. Given the wide variety of intermediate hosts (vectors) of the parasite that can infect dogs, it is practically impossible to design effective prophylaxis.
Stomach and Intestine
Strongyloidosis, or hookworm infestation, is mainly due to Uncinaria stenocephala, the most common hookworm in France; to Ancylostoma caninum, particularly in torrid zones; and Ancylostoma braziliense in tropical countries. These parasites affect primarily animals living in groups, which is why in French an infestation is sometimes called "pack dog anemia," but other dogs may be infested as well. Hookworm larvae of the Ancylostoma genus penetrate through the skin or are ingested by puppies along with the bitch's milk. The infestation has several stages corresponding to larval migrations within the body. It begins with a cutaneous phase: small lesions appear on the dog's abdomen, then disappear spontaneously within about ten days.
The adults develop in the small intestine, which causes digestive symptoms such as alternating diarrhea and constipation, then the appearance of persistent diarrhea with a fetid odor. Finally, the dog's general health worsens due to anemia. In its severe forms, the disease may lead to death, while in more benign forms spontaneous recovery is possible.
The parasites take blood: the adult form attaches to the intestinal mucous membrane, eats a small amount of blood, and has the same effect as bleeding the dog. The parasites probably also have a toxic effect, and affect the immune system as well: As a result, there is a stronger skin reaction on reinfestation, which hinders larval migration. In this way, dogs can become fairly resistant to these hookworms.
The primary means of prevention in areas with groups of dogs is to disinfect the area. Pregnant bitches can be given a preventive treatment of fenbendazole, which destroys the larvae. Puppies can also be treated once a week from the age of ten to forty-five days, then again at eight weeks and twelve weeks in areas where these parasites are prevalent.
Small Intestine
Parasites of the small intestine include nematodes (roundworms) of the Ascaris family (Toxascaris leonina) and the Toxocara family (Toxocara canis). T. canis can be transmitted to humans. These parasites infest mainly young dogs less than a year old. The puppies ingest embryonic eggs in their drinking water or food, or the eggs are transmitted from the mother to the puppies either in utero or via the milk. Dogs that are in poor general health are more susceptible, particularly animals suffering from certain nutritional deficiencies. Massive infestation causes general symptoms such as slow growth, weight loss, and a high mortality rate in three- to seven-week-old puppies that were massively infested before birth.
Of course, the puppies display mainly digestive symptoms: diarrhea interspersed with periods of constipation, vomiting (to get rid of some of the parasites), and a distinctly pot-bellied appearance. Complications may also occur in the form of intestinal blockage (by a clump of worms) or even intestinal perforation leading to hemorrhage or peritonitis. In addition to causing these symptoms, the parasites ingest blood and some of the intestinal contents, which both contain constituents that are essential to the puppy's growth. Diagnosis is usually straightforward: the puppy's overall health is poor, its abdomen distended, and it sheds parasites in its stools or by vomiting. Analysis of a stool sample can sometimes help with the diagnosis. Many parasiticides are available, the most effective being pyrantel pamoate, nitroscanate, and ivermectin. Preventive measures include systematic treatment of young dogs and destruction of the adult worms present in the mother. It is extremely difficult to destroy eggs in the environment, as they are highly resistant.
Cestodes can also parasitize this portion of the digestive tract. These tapeworms, such as Dipylidium caninum, are transmitted when fleas are ingested. They affect dogs of all ages, leading to significant anal pruritis that causes the dog to rub its posterior on the ground. Associated digestive symptoms include the elimination of segments of the parasite (which look like grains of rice) in the stools, which may have the appearance of diarrhea. Reinfestation is common, facilitated by the fact that eggs can stick to the dog's hair and be ingested. The spoliatory effect is very slight: The parasites' main effect is to cause irritation and swelling of the anal glands.
Prophylaxis consists of first eliminating intermediate hosts, both fleas and, to a lesser extent, lice. Use of specific anti-cestode treatments such as praziquantel in the infested animals is then recommended. Multi-purpose anthelminthics such as nitroscanate can also be effective.
Large Intestine
This portion of the digestive tract, namely the cecum and colon, is parasitized mainly by nematodes of the genus Trichuris. Dogs become infested by ingesting eggs present in the environment, with adults seeming to be affected more often. A massive infestation leads to symptoms such as diarrhea (which can be bloody), anemia, and obvious weight loss. These whipworms siphon off blood and cause lesions in which bacteria can develop. Diagnosis depends on a stool analysis, which reveals the presence of parasite eggs in the dog's feces.
Treatment is by administration of benzimidazoles such as flubendazole for three consecutive days, or of febantel for the same length of time. Reinfestation occurs very easily, however, so the owner must ensure that the facilities are clean and the food is sanitary.
Worming
Puppies can be wormed after they are two weeks old, as a preventive measure. A multi-purpose vermifuge is used, usually consisting of a mixture of several anthelminthics providing a broad spectrum of protection. The dose should be adjusted for the puppy's weight. The dog is then treated once a month until it is six months old, then from two to four times per year depending on whether it goes out frequently or not.
Stool analysis can also reveal worm eggs, and the worms can then be more specifically targeted by choosing the best anthelminthic for the type of worm observed. The dog's characteristics should be taken into account when deciding how to administer the vermifuge, whether as pills, paste or liquid. Some can be given in one dose, and some require several, which will also influence the decision.
Regular worming is essential, particularly if several dogs live together and in cases where there is a risk that the worms may be transmitted to humans.
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