Pets with intestinal worms experience a range of symptoms from anemia, malnutrition, and death to no symptoms at all. Intestinal worms compete with the pet for nutrients so that a pet with a heavy worm burden looks malnourished and has a swollen belly. The hair is often dry, dull, and coarse. There can be mucoid discharge from the eyes. Pets can have diarrhea and abdominal pain. Over time, they lose weight.
Pets with parasites that suck blood (hookworms) or cause blood loss because they damage the intestinal wall (whipworms) experience anemia. Anemic pets have pale mucous membranes and a rapid heart beat.

To recap, pets with worms may display the following signs and symptoms:

• Weight loss
• Dull coat
• Swollen belly
• Worms in stool
• Anemia

How are dogs and cats diagnosed with worms?
Fecal exams are done routinely at veterinary clinics. The latest research shows that if the fecal samples diagnosed as negative are sent on to a commercial pathology lab, 75% are found to contain worm eggs. Because of this new research, many veterinary clinics have begun recommending that pets receive deworming medication even when they have negative fecal samples.
To accurately diagnose worms the following tests are done on fresh feces: direct smear, fecal float, Baermann and, fecal culture. With a direct smear test, feces are combined with saline to identify giardia in the trophozoite stage. A fecal float is prepared to look for cryptosporidium, giardia cysts, trematodes, and thorny-headed worms (acanthocephalans). To prepare a fecal float, feces is mixed with a special solution, such as zinc sulfate, and put into a centrifuge. Even with this painstaking technique, not all parasite eggs are found, because not all eggs float to the top of the solution. Centrifuged material is examined immediately because fragile parasites are rapidly destroyed. With the Baermann technique, feces is suspended in a funnel and solution is added so that the parasites swim out of the stool. A fecal culture is used to identify pathogenic bacteria, such as salmonella, rather than to identify worms.

Here are examples of what your veterinarian can find using these techniques:

• Direct smear for giardia trophozites
• Centrifuged sediment for fluke eggs (Paragonimus) because fluke eggs are too heavy to float
• The top of the centrifuged material for nematode ova, Capillaria eggs, Giardia cysts, coccidia (Cryptosporidia, Isospora or Eimeria) oocysts because they float well
• Baermann technique for Aelurostrongylus
• Fecal culture for salmonella and clostridia

These factors interfere with obtaining an accurate diagnosis from a fecal sample:

• Using old feces rather than fresh feces that is still at body temperature and less than 1 hour old
• Using feces that remained on the ground more than a few minutes
• Not looking at the centrifuged solution within 10 minutes

What if the fecal tests are negative?
Ordinary fecal tests identify worm eggs. Puppies and kittens should be dewormed regardless of fecal tests because they have worms that have not matured to the point of producing eggs. The fecal tests will be negative, but the puppies and kittens are infected.
Most adults with negative fecal tests should also be dewormed because the Companion Animal Parasite Council says that about 75% of pets with negative fecal tests have worms that are found when the samples are tested at universities and parasitology laboratories.