Final answer:
Giardia lamblia and Cryptosporidium parvum are common protozoan parasites that cause severe diarrhea in puppies, often transmitted through contaminated water and feces.
Step-by-step explanation:
Protozoan Infections in Puppies
One common protozoan infection in puppies that results in severe diarrhea or loose stools is caused by Giardia lamblia. This intestinal protozoan parasite can infect both humans and other mammals and is often spotted under scanning electron microscopy as demonstrated in Figure 23.30. Giardia is typically transmitted through contaminated water and once ingested, it reaches the lining of the small intestine causing an onset of symptoms, including explosive and watery diarrhea, within seven to ten days.
Another significant protozoan is Cryptosporidium parvum, which causes cryptosporidiosis, a condition common in animals that can also infect humans and is known for its role in outbreaks of diarrhea. Likewise, it's commonly spread through feces and can contaminate water and food sources, leading to human and animal illnesses. Proper rehydration therapy is crucial for treating the dehydration caused by protozoan infections. Simultaneously, drug-specific treatments targeted at protozoans are also essential to manage these infections.