Parvovirus is one of the deadliest diseases in the dog population, particularly among puppies. Gaining entry through the mouth, the virus attacks the digestive tract and kills cells that are critical in the absorption of nutrients. Severe fluid loss through diarrhea and vomiting can lead to shock and death. Parvo also temporarily affects a dog's immune system.
Parvovirus is spread through contact with feces containing the virus. The virus is known to survive in the environment and on inanimate objects - such as clothing, food pans, and cage floors - for up to 2 years in the right conditions.
Whipworms are blood suckers, tunneling into the wall of the intestine for their blood meals. Dogs may not show any signs, but when they do show signs, diarrhea and weight loss are usually observed. In large numbers, these parasites can cause anemia and even death. Whipworms can be difficult to diagnose due to long life cycles, eggs are shed intermittently, and the dense eggs are difficult to detect on fecal tests.
Adult worms in a dog's cecum produce eggs that are passed in the feces. The eggs must remain in the soil for 9-21 days to mature and be capable of causing infection. A dog becomes infected by ingesting whipworm eggs from the environment.
Hookworms are blood suckers attaching to the intestinal wall where they suck plugs of the intestinal tissue into their mouth structures. Anemia and/or intense inflammation can result. In the intestine, the adults produce eggs that pass into the feces. In 1-2 weeks, the eggs hatch and the larvae are released. These larvae live in the soil and wait for an animal to come along. Larvae may be ingested through contaminated sources in the environment, or from prey animals. Larvae may also infect animals by burrowing through the skin. A nursing dog may also pass the larvae to her nursing puppies. Hookworm infections can be passed to humans.
Roundworms (ascarids) can affect the lungs and the digestive system, with typical signs being vomiting and diarrhea. Puppies may have a distended abdomen, poor haircoat, and be underweight. Roundworms can also be spread to humans.
Prompt removal and disposal of dog stools is the first step in controlling the spread of roundworms. Of the three types of roundworms affecting dogs, Toxocara canis has the most complex life cycle. It begins when the worms' eggs pass out in the infected animal's feces. These eggs survive in the environment and are later ingested by another dog. The larvae are released from the eggs and enter the wall of the new host's small intestine and eventually migrate through the liver and lungs. Finally they re-enter the intestine where they mature and mate, and eggs are passed again in the feces.
Giardia are one-celled parasites that can cause diarrhea in dogs and cats. Infection with Giardia is often difficult to diagnose and treat effectively.
A dog becomes infected by eating the cyst form of the parasite. In the small intestine, the cyst opens and releases an active form called a trophozoite. These have flagella, hair-like structures that whip back and forth allowing them to move around. They attach to the intestinal wall and reproduce by dividing in two. After an unknown number of divisions, this form develops a wall around itself (encysts) and is passed in the feces. The Giardia in the feces can contaminate the environment and water and infect other animals and people.
Coccidia are also one-celled parasites that can cause diarrhea, especially in puppies & kittens.
Young animals are frequently exposed to their mother's feces. If the mother is shedding the infective organisms in her feces, then the young animals will likely ingest them and coccidia will mature within their intestines. Young animals tend to have more severe illness associated with coccidia infection.
The best way to prevent these, and the many bacterial infections dogs can acquire from stools, is to remove feces immediately and keep your dog current on his vaccinations, fecal examinations and deworming. Also, pick up waste before a rain, which breaks up or scatters the feces and allows the worms or germs to spread into the environment.