Heartworm's
Heartworm (Dirofilaria immitis) is a fairly large worm up to 14 inches long that, in adulthood, lives in the heart and pulmonary arteries of an infected dog. Dogs acquire this infection through mosquito bites as mosquitoes readily pick up larval heartworm's from infected dogs and carry them to new dogs. Some geographic areas have severe heartworm problems while other areas have none. In order for the parasite to establish its presence in an area, the following conditions must be met:
- Types of mosquitoes capable of carrying larval heartworm's must be present
- The weather must be warm enough to allow heartworm larval development within the mosquito
- There must be infected dogs (or coyotes) in the area
- There must be vulnerable host dogs in the area
When these conditions come together, an area becomes endemic for heartworm disease. Monthly heartworm treatment is strongly advised.
Tapeworms
The adult tapeworm (Dipylidium caninum) lives in the small intestine of the dog or cat. It is hooked onto the intestinal wall by a structure called a rostellum which is sort of like a hat with hooks on it. The tapeworm also has six rows of teeth to grab on with. Most people are confused about the size of a tapeworm because they only see its segments which are small; the entire tapeworm is usually 6 inches or more. Once docked like a boat to the host intestinal wall, the tapeworm begins to grow a long tail. (The tapeworm’s body is basically a head segment to hold on with, a neck, and many tail segments). Each segment making up the tail is like a separate independent body, with an independent digestive system and reproductive tract. The tapeworm absorbs nutrients through its skin as the food being digested by the host flows past it. Older segments are pushed toward the tip of the tail as new segments are produced by the neckpiece. By the time a segment has reached the end of the tail, only the reproductive tract is left. When the segment drops off, it is basically just a sac of tapeworm eggs. This segment is white and able to move when it is fresh and, at this time, looks like a grain of white rice. As the segment dries, it looks more like a sesame seed.
Tapeworms are acquired by the dog eating a flea. It takes 3 weeks from the time the flea is swallowed to the time tapeworm segments appear on the pet’s rear end or stool.
Hookworms
The hookworm (Ancylostoma caninum, Ancylostoma braziliense) is one of the classical internal parasites of puppies. Hookworm infection has several special features that are of interest to us as the caretakers of dogs:
- Hookworms can be transmitted to unborn pups.
- Hookworms can infect humans.
The adult hookworm lives in the small intestine of its host. It hangs on to the intestinal wall using its six sharp teeth and unlike other worms that just absorb the digested food through their skin as it passes by; the hookworm drinks its host's blood. The adult worm lives and mates within the host and ultimately, the female worm produces eggs. Hookworm eggs are released into the intestinal contents and passed into the world mixed in with the host's stool.
Infected puppies are commonly pale, weak, and have long-standing deficiencies. They may or may not have diarrhea.
Roundworms
There are two species of roundworms affecting dogs and puppies: Toxocara canis and Toxascaris leonina. Both are treated with the same medication protocol so when eggs are seen on a fecal flotation exam, it is not necessary to determine which species is present. Roundworm infection can have numerous negative effects. It is a common cause of diarrhea in young animals and can cause vomiting as well. Sometimes the worms themselves are vomited up which can be alarming as they can be quite large which females reaching lengths of up to seven inches. The worms consume the host's food and can lead to unthriftiness and a classical pot-bellied appearance. Very heavy infections can lead to pneumonia as the worms migrate and, if there are enough worms, the intestine can actually become obstructed. Roundworms are long, white and described as looking like spaghetti.
Whipworm's
The whipworm of dogs (Trichuris vulpis) is substantially smaller than the other worms (a mere 30 to 50 mm in length, about a half inch maximum) and is rarely seen as it lives in the cecum (the part of the large intestine where the small and large intestine meet). The "head" (or more accurately the digestive end of the worm) is skinny vs. its stout tail (or reproductive end) which gives the worm a whip shape, hence the name.
A few whipworm's generally do not pose a problem for the host but if large numbers of worms are present embedding themselves in the large intestine tissue, tremendous inflammation can result leading to a bloody, gooey diarrhea. Usually there is not enough blood loss to be dangerous but the diarrhea readily becomes chronic and hard to control.
