Whipworms, or Trichuris vulpis, are common, bothersome intestinal parasites of domestic dogs. They embed themselves in the sensitive lining of a dog's large intestine, where they feed on its blood and deplete it of iron, electrolytes and other essential nutrients. Whipworms are widely distributed throughout the United States and other parts of North America. Adults generally range from two to four inches in length. They spend much of their life cycle in a dog's cecum, which is the junction between the small and large intestines. They also spend time in the large intestine itself. The medical name for infection with whipworms is "trichuriasis". Thankfully, unlike some other parasites, canine whipworms do not infect people.
Causes of Whipworm Infection in Dogs
Dogs infected with adult whipworms pass the parasites' eggs in their feces, contaminating the soil, grass and other areas that their stool comes into contact with. Adult females can lay thousands of eggs in one day. These eggs are extremely resistant to environmental conditions, including temperature and weather extremes. They can easily survive in the environment - and remain infective – almost indefinitely. For months or even years, whipworm eggs from the feces of infected dogs are the prime source of infection to other canine passers-by. Dogs become infected by eating the whipworm eggs. This commonly happens when a dog walks through a contaminated area and then licks its paws and fur during self-grooming.
Once whipworm eggs get into a dog, they settle in its upper digestive tract, usually hatching in the small intestine. Newly-hatched larvae burrow their slender, "whip-like" heads into the dog's small intestinal lining (called the intestinal mucosa), where they lodge, feed and grow. For the first week or two after hatching, the larvae usually don't cause noticeable symptoms in the host dog. Eventually, however, adolescent whipworms migrate out of the small intestine and move into the cecum and large intestine, where they mature over a matter of months. The cecum is the part of the digestive tract that connects the small intestine to the large intestine. The large intestine is also called the colon, or the lower bowel. Whipworms infiltrate the tender lining of the lower digestive tract and dine on the dog's tissues and bodily fluids. These blood-sucking parasites cause varying degrees of gastrointestinal irritation and inflammation, which in some cases becomes quite severe.
Prevention of Whipworms
Most over-the-counter de-worming medications do not effectively prevent or resolve whipworm infections The best way to control these parasites is to use prescription de-wormers, and it is well worth a trip to the veterinarian to obtain them. Milbemycin oxime reportedly is an excellent preventative against whipworms and a number of other parasites, including mosquitoes. It is available in oral form. Since whipworm eggs are extremely hardy, de-worming protocols should be followed to a tee upon the recommendation of the dog's veterinarian. Dogs that are not on a regular de-worming program probably should not be taken to areas frequented by dogs whose health status is unknown, particularly areas with a lot of obvious fecal contamination. Unfortunately, sometimes this includes public dog parks, city parks, playgrounds and similar areas, where most dog owners enjoy taking their dogs.
Good environmental hygiene is important to controlling the spread of both internal and external parasites. Kennels, crates, dog runs, yards and other areas where dogs urinate and defecate should be cleaned and disinfected regularly. A high-quality diet, regular moderate exercise and free access to fresh water can also help to keep companion dogs healthy, happy and fit.
The main cause of whipworm infection is ingestion of parasite eggs that are expelled in fecal matter of infected dogs. Fortunately, there are several good options for treating dogs with whipworms. Some of these are not appropriate for use in very young puppies or in pregnant females. Treatment should always be accompanied by nurturing supportive care and a healthy diet.
How Whipworms Affect Dogs
Whipworms tend to affect adult dogs more often and more severely than they do puppies, which is somewhat unusual among canine internal parasites. These are large worms that spend most of their lives in a dog's lower digestive tract, where they burrow into the lining of the large bowel wall and feed on the dog's tissues, blood and other bodily fluids. Many dogs with whipworms show no signs of discomfort or distress. However, others develop mild to severe symptoms that usually are attributed to large bowel inflammation. Belly-aches, diarrhea and abdominal cramping are the hallmarks of whipworm infection in dogs.
Symptoms of Whipworms
Owners of dogs that are infected with whipworms may notice none, one or more of the following signs:
Frequent defecation ("pooping" more often than usual)
Urgency to defecate
Straining to defecate (tenesmus)
Loose, watery stool (+/-mucus; +/- fresh blood)
Severe diarrhea (+/- mucus; +/- fresh blood)
Loss of appetite (inappetence; anorexia)
Ill thrift; failure to thrive
Electrolyte imbalances, similar to those in dogs with Addison's disease (hypoadrenocorticism)
Seizures (probably due to profoundly low levels of circulating sodium)
Abdominal pain (variable; intermittent)
Licking at the belly or flank area
Anemia (pale mucous membranes; pallor; weakness; caused by abnormally low numbers of circulating red blood cells)
Dogs at Increased Risk
There is no particular gender, breed or age predisposition for whipworm infection, although for some reason it seems to be more common in mature dogs. Dogs housed in high-density kennel situations, in outdoor runs, on dirt floors or in areas surrounded by a build-up of fecal matter have a greater chance of becoming infected with these parasites, as do dogs that are allowed to roam freely.
How Whipworms are Diagnosed
Whipworms are not particularly difficult for a veterinarian to diagnose. Sometimes, they are only detected during a routine fecal examination. Dogs brought to a veterinary clinic with gastrointestinal symptoms will be given a thorough physical examination and typically will have blood drawn for routine blood work, including a complete blood count and a serum biochemistry profile. The veterinarian will take a history from the dog's owner and may also recommend a urinalysis as part of the initial work-up. The results of these tests may indicate an internal parasite infection. If the dog has suffered from prolonged severe diarrhea, it may be dehydrated, and its blood sodium-to-potassium ratio may be off as well.
The best and most common way to diagnose whipworms is through a procedure called "fecal floatation." This test is performed on a small fresh fecal sample, which usually is obtained manually at the veterinary clinic. The test can also be done on a fresh sample brought in by the owner. The fecal specimen is mixed with a solution that has specific chemical properties that encourage parasite eggs to float to its surface. Some common flotation solutions are sodium nitrate, zinc sulfate and "Sheather's solution," which is a sugar solution used by many commercial veterinary laboratories.
After the solution and the fecal sample are combined, the mixture is strained into a test tube. A glass coverslip is placed on top of the tube, touching the liquid mixture. The tube is placed in a centrifuge and mixed mechanically at a set speed for a set period of time, then rested to allow time for the eggs to float to the surface. This is the procedure for most types of centrifuge instruments; with other machines, the laboratory personnel will spin the sample before covering it. Either way, after an appropriate resting period, the coverslip will be removed, placed wet-side down onto a clean glass slide and evaluated under a microscope.
The eggs of a number of different internal parasites can be identified by this procedure. In the case of whipworms, identifiable eggs are shed in low numbers and only intermittently. As a result, a single negative fecal floatation does not necessarily mean that the patient is free from whipworms. Veterinarians often recommend performing a series of fecal floatations over several days or weeks, before whipworm infection is ruled out. Of course, a positive fecal floatation test, especially if a large number of characteristic eggs are identified, is diagnostic of whipworms.
Some of the symptoms of Addison's disease (hypoadrenocorticism) can closely mimic those of whipworm infestation, especially those caused by low levels of circulating sodium and potassium. Because of this, the dog's veterinarian may suggest performing an ACTH response test to rule out Addison's. ACTH stands for adrenocorticotropic hormone. It is produced and secreted in the brain by the pituitary gland and normally stimulates the adrenal glands to secrete key hormones, including corticosteroids, into the bloodstream. The cortisol levels in dogs with whipworms will rise after administration of ACTH, whereas in dogs with Addison's disease the ACTH will have no measurable effect.
Endoscopy can be used to detect the presence of whipworms in the large bowel. This procedure, also known as a colonoscopy, can help the veterinarian actually see the adult parasites through a tiny camera located on the end tip of the instrument. However, endoscopy is fairly expensive and normally is not necessary to diagnose whipworm infection in dogs.
In a mild case of suspected whipworm infection, the attending veterinarian may elect to treat the dog with an anti-parasitic medication even before a definitive diagnosis of whipworms or any other gastrointestinal parasite is reached. This can be an effective, relatively inexpensive and safe way to both diagnose and treat the condition in one fell swoop. Currently, the drug most commonly used in this fashion is fenbendazole.
Adult whipworms are not particularly difficult to treat in dogs. However, it can be hard to eliminate whipworm eggs from the environment. Bleach, steam and sunlight are helpful, especially in high-density kennel situations. The goals of treating whipworms are to eradicate the parasites from the dog's digestive tract, eliminate eggs from the environment and prevent cycles of reinfection.
A number of effective treatments are available for dogs with whipworms, some of which are not appropriate for use in very young puppies or pregnant females. Any medical treatment should be accompanied by nurturing supportive care, including good nutrition, free access to fresh water and a safe, quiet, warm, well-bedded living environment. In cases of severe whipworm infestation, the animal may need to be hospitalized so that it can receive intravenous fluids, electrolytes, iron, oxygen and/or other nutritional support.
The array of drugs currently available to treat dogs with whipworms includes fenbendazole (Panacur; probably the preferred go-to-treatment according to many authorities; reported to be safe to use during pregnancy); febantel; praziquantel/pyrantel/febantel (Drontal Plus; not currently recommended for use in pregnant dogs); diethylcarbamazine/oxibendazole (Filaribits Plus; reported to have caused liver/hepatic injury in some dogs); and milbemycin oxime (Interceptor; reportedly has good results as a preventive when used monthly for chronic, recurrent infections; dogs receiving milbemycin oxime should have a heartworm test before it is administered).
Treatment of whipworms normally is done once monthly for 3 months, with frequent fecal rechecks at the veterinary clinic to be sure that the dog has not become reinfected. Most of these medications are administered orally or topically. The precise de-worming regimen can vary depending upon which drugs or combination of drugs is being used. When a dog has been diagnosed with whipworms, it is important for its owner to follow the veterinarian's de-worming protocol closely.
The prognosis for dogs with whipworms is generally quite good, as long as they receive appropriate and timely treatment. Unfortunately, because the eggs of these parasites are so hardy and can survive for so long in most environments, reinfection is common. Dogs do not become resistant to whipworm infection following their first infection.