Warning: Worms Can Hurt You and Your Pet!

That cute little potbelly that many puppies seem to have could be caused by worms! Most dogs and cats acquire some type of intestinal parasite during their lifetime, and these worms can not only be annoying, but can cause debilitating medical problems, especially in young animals. It is important to remove these parasites for the sake of your pet, and also because humans can become infected.

Roundworms are probably the most common intestinal parasite that infects companion animals. According to Dr. Allan Paul, a veterinary parasitologist at the University of Illinois College of Veterinary Medicine in Urbana, "Most parasite eggs require a minimum temperature in order to develop into an actively infectious state. For this reason, they are most likely to be spread during the spring and summer."

Roundworm eggs are excreted in the faeces in dogs and cats. They are spread when animals come in contact with the faeces or soil. These worms can also be transmitted across the placenta to puppies before they are born and spread from mother cats to kittens through infected milk. 

Once they develop into their adult form, roundworms live in the intestine and feed off the food the dog or cat has eaten. They are very prolific. One female can lay up to 200,000 eggs per day. This means that a large number of worms can develop in a short period. 

Infestation can cause diarrhoea, vomiting, and the characteristic potbelly seen in many puppies. A rough hair coat and generally unhealthy appearance are other signs. These worms are usually not a serious problem for adult animals, but can be life-threatening to puppies and kittens that may experience severe dehydration as a result of vomiting and diarrhoea.

Hookworms and whipworms are other common parasites in dogs and cats. Instead of feeding off digesting material in the intestine, these parasites attach to the intestinal lining and feed by sucking the blood of the infected animal. A heavy infestation of either of these parasites can cause severe anaemia.

Hookworms are more common than whipworms. Hookworms feed at several places in the intestine each day, injecting an anti-coagulant that prevents clotting. This means that after the hookworm detaches from the intestinal wall, that spot continues to bleed, which can cause a black, tarry-looking stool. Hookworms can be transmitted through oral ingestion of eggs in fecal material and also by penetrating the skin directly. 

Your veterinarian can diagnose roundworms, hookworms, and whipworms by doing a faecal examination in which the eggs of the worm are identified. The worms can easily be removed by the administration of a de-wormer prescribed by your veterinarian. 

It is important to treat intestinal parasites in your pet because they can be transmitted to humans. Roundworms and hookworms do not mature in the intestine in human beings. Instead, they remain in an immature larval state and migrate throughout the tissues of the body. They can cause liver and lung damage, skin rashes, and even blindness and permanent neurological damage. Children are most at risk because they may play in infested areas and may ingest infected material. The best way to prevent infection is to make sure your pets are parasite free and your children always clean up properly after playing outside.

To prevent problems with intestinal parasites for your pet and for you, consult your local veterinarian on de-worming and parasite control. 

Jennifer Stone - Information Specialist
University of Illinois College of Veterinary Medicine


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.

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.



Dogs, cats and most other creatures for that matter are susceptible to having internal parasites. Now, when we discuss internal parasites, most people think of worms, and pets do get worms. But they also often have microscopic one-cell organisms such as Coccidia and Giardia which can equally upset the digestive process.

Parasites can be picked-up by licking the ground, drinking contaminated water, and from the mother dog/cat to the offspring before or after birth! Fleas, rodents and birds can also give your pet tapeworms. So one can see that it isn't too hard for your pet to become infested. It is also important to realize that not all pets that have parasites will be thin and have diarrhoea. Many look quite normal on the outside.

As a dog owner, it’s important to know about the different types of worms and the effects they have on a dog’s health. And since people can become infected with roundworms and hookworms, it’s that much more important to keep your dog parasite-free. Here are some basic facts about the more common parasites to help:

ROUNDWORMS (Toxocara canis, Toxascaris leonina) are the most common type of worm to infect the animal kingdom. These worms are usually 2 – 4 inches long, tan or white “spaghetti-like” creatures with tapered ends. If a roundworm burden is heavy, a dog may vomit these worms or pass them (whole) in the stool. Roundworms can cause vomiting and diarrhoea and can have an effect on a dog’s overall general health and appearance. Puppies infected with roundworms will have a “potbellied” (bloated) look to them. Roundworms can become so numerous that they can cause an intestinal blockage and stool cannot pass. As mentioned above, roundworms are zoonotic (can be transferred to humans) and can cause an infection known as “Visceral Larva Migrans”, which may result in possible inflammation of muscle tissue and blindness. Anthelmintics (de-wormers) that are frequently used to treat roundworms are pyrantel pamoate, fenbendazole and piperazine

HOOKWORMS (Ancylostoma caninium) are blood-sucking intestinal parasites and have the ability to cause anaemia (and sometimes death) in puppies and adult dogs. Hookworms cannot be seen by the naked eye, and the severity of adverse effects will depend on the amount of worms in the intestine, the animal’s overall health and age. In humans, hookworms can cause “Cutaneous Larva Migrans”, commonly called “creeping eruption”. The hookworm larvae will burrow into the skin of a human’s foot or leg causing a linear, red lesion, which is intensely itchy. This parasite has also been known to cause chronic intestinal bleeding, abdominal pain and diarrhoea in small children. De-worming medications usually include pyrantel pamoate and fenbendazole.

TAPEWORMS (Dipylidium caninum) are the other parasites that can be seen by the dog owner. Actually, what the dog owner with observe is tapeworm segments that have broken off from the adult parasite attached to the lining of the dog’s intestinal tract. These tapeworm pieces are ¼ - ½ inch in length, are usually white and are usually seen (while still alive) contracting and expanding around the dog’s rectum or on a dog’s stool immediately after elimination. Once these segments die, they will appear like a grain of uncooked wild rice or a sesame seed and are often found in the dog’s bedding. The most common route of infection occurs when the dog swallows a flea that is carrying the parasite’s eggs. Tapeworms cannot be directly transmitted from dogs to humans but small children could accidentally ingest flea larvae or pupae on the floor containing an immature tapeworm and get a tapeworm infection. De-worming can be done by either oral medication or by injection and the most common antiparasitic agent used is praziquantel another is epsiprantel.

WHIPWORM (Trichuris vulpis) is one of the less notable parasites and it cannot be seen by the dog owner. Unfortunately, this particular parasite is the most difficult to eradicate and control and the symptoms may include severe diarrhoea, flatulence, loss of weight and general overall condition. The anthelmintic for whipworm most commonly prescribed is fenbendazole (Panacur). One note of importance to pet owners, monthly doses of the common heartworm preventative medication containing milbemycin oxime will help to keep these parasites under control.

COCCIDA (Isopora canis) is not a worm, but a single cell microscopic organism that will cause “havoc” in a dog’s intestinal tract when present in great numbers. This protozoa will cause watery diarrhoea in young and susceptible animals that have immature or compromised immune systems; in some cases, the diarrhoea can be severe enough to be life threatening. Eradication of this parasite is usually successful with a daily dose of a sulfonamide antimicrobial agent.

Summary of important information about specific life cycles

   Dipylidium caninum - dog & cat tapeworm Babesis canis - dogs
Route(s) of entry to the host Ingestion of intermediate hosts (fleas and lice) containing cysticercoids. Injection of sporozoites by feeding female ticks (Rhipicephalus)
Predilection site in the definitive host Small intestine Red cells (asexual reproduction)
Route to the predilection site Direct development in the small intestine after  ingestion of intermediate hosts.  Invasion of red cells by sporozoites
Route of exit from the host In the faeces of the host Infected red cells are ingested by feeding ticks
Stage entering the host (infective stage) Cysticercoid Sporozoites
Stage leaving the host (diagnostic stage) Egg Trophozoite in host red blood cells

Common - seen regular (at least several times per year)

Anclystoma caninum (Canine Hookworm)
Cuterebra spp. (Rodent Bot Fly)
Dipylidium caninum (Double-pore Tapeworm)
Dirofilaria immitis (Canine Heartworm)
Giardia duodenalis (Giardiasis)
Isospora canis (Coccidia)
Isospora ohionensis (Coccidia)
Taenia pisiformis (Tapeworm)
Toxascaris leonina (Roundworm (Ascarid))
Toxocara canis (Common Roundworm (Ascarid) of Dogs)
Trichuris vulpis (The whipworm of dogs)

Uncommon - seen occasionally (once every year or two)

Babesia canis (Babesiosis)
Baylisacaris procyonis
Capillaria aerophila (Lungworm of dogs and cats)
Capillaria boehmi (Nasal worm of dogs and foxes)
Capillaria plica (Bladder worm of dogs and cats)
Crenosoma vulpis (Fox lungworm)
Cryptosporidium parvum
Dipetalonema reconditum
Diphyllobothrium latum (Broad Fish Tapeworm)
Leishmania spp. (Visceral Leishmaniasis)
Neospora caninum
Paragonomus kellicotti (Lung fluke)
Physaloptera spp. (Stomach worm)
Sarcocystis cruzi 
Strongyloides stercoralis
Trichomonas spp.
Uncinaria stenocephala (The Northern hookworm of dogs)

Rare - not seen or seen only once or twice in the last 15 years

Ancylostoma brazilensis
Babesia gibsoni
Balantidium coli
Dioctophyme renale
Dracunculus insigni
Echinococcus granulosus
Echinococcus multilocularis
Entamoeba histolytica
Filaroides hirthi
Oslerus (Filaroides) osleri
Heterobilharzia americana
Macracanthorhynchus ingens
Mesocestoides corti
Nanophyetus samincola
Parametorchius complexus
Platynosomum fastosum
Spirocerca lupi 
Spriometra mansonoides 
Taenia hydatigena
Taenia ovis
Taenia multiceps
Taenia serialis
Thelazia californiensis
Trichinella spiralis
Trypanosoma cruzi

There is an extremely informative site here with in-depth information.
University of Pennsylvania School of Veterinary Medicine



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