Ascarids which are large roundworms are common in dogs, particularly in puppies. The most common species is Toxocara canis. The larvae of Toxocara canis can migrate in people. On occasion, the infection can be fatal in young puppies. Toxacaris leonina is not as common, and usually affects older dogs.
Toxocara canis in puppies is usually transmitted to the fetus through the placenta. Puppies one week old can have the worms in the intestines. Puppies can also be infected when they are nursing. If pups who are under three months old eat eggs that have been in the environment for a minimum of four weeks, the eggs will hatch in the puppy’s system. The larvae will enter the intestinal wall and move through the liver. They will reach the lungs through the blood stream. They can be coughed up, swallowed again and then mature to adults who will produce eggs in the small intestine. Many larvae will move through the blood stream tho other areas of the body and can remain in the tissues for years in an inactive form. These larvae can become active if the immune system is suppressed. Adult dogs have some natural resistance to the infection.
Although in the female, the resistance is partially suppressed near the birth of a litter. The inactive larvae can become active. They will enter the pups through the placenta and some will move to the mammary tissues. The larvae in the mammary tissues can then enter the puppies through the colostrum and milk. The female herself may be actively infected and pass a large number of eggs in the fecal matter.
The first sign of roundworm infection in a young dog is condition loss and a lack of growth. The coat will be dull and the animal may look potbellied. The worms can be vomited and passed in the feces. In the early stages of an infection, the migrating larvae can cause pneumonia and there may be coughing. The animal may have mucus laden diarrhea. Diagnosis is confirm by the presence of roundworm eggs in the feces.
There are a number of treatments available to treat a roundworm infection. The preventive treatment programs for heartworm infection can also be used to control roundworm infection. It is possible to reduce the transmission of infection from the mother to the puppies by administering a program of anti-parasitic drugs during pregnancy and after birth. If this is not done then the pups should be treated as early as possible. Treatment should be administered at two weeks of age and repeated every two to three weeks until the pup is three months old. After this, treatment should be given every month until the pup is six months old. Nursing mothers should be treated on the same schedule as the pups. The veterinarian will prescribe an appropriate medication for this infection.