This is a human retina with ocular larval migrans due to Toxocara canis ingestion.
When people ingest T. canis eggs, infections are usually asymptomatic, but cases of ocular and visceral larval migrans do sometimes occur.
When adult non-pregnant dogs eat T. canis eggs, there is arrested development in the tissues. But when pregnant bitches eat T. canis eggs, infection can lead to transplacental transfer of infection to fetal puppies or transmammary transfer to nursing pups.
Clinical signs of T. canis infection in puppies include failure to thrive, pot-bellied appearance, dull coat, and mucoid diarrhea. Puppies with eosinophilic pneumonia will cough.
Dx: Sometimes worms are seen in vomit or feces. Definitive Dx involves identifying the spherical, pitted-shelled eggs of Toxocara spp. (T. canis and T. cati, both zoonotic) from the oval, smooth-shelled eggs of Toxascaris leonina (NOT zoonotic).
Click here to compare both types of eggs under the microscope. This is important because of the public health significance of T. canis and T. cati, which can cause visceral and ocular larva migrans.
You should advise owner on zoonotic nature of the parasite! Click here to see a great resource from the CDC.
Rx: A wide range of anthelmintics are effective (e.g., fenbendazole, pyrantel, milbemycin, ivermectin).
Prevention: Treat bitches with one of the recommended therapeutic regimens to minimize transplacental or transmammary transfer.
Otherwise, treat pups starting ~2 weeks after birth, every 2 weeks until 2 months of age, and then monthly until 6 months of age.
Refs: Bowman and Georgi, Parasitology for Vets, 9th ed., CDC Guidelines for Vets: Prevention of Zoonotic Transmission of Ascarids and Hookworms of Dogs and Cats, Coté, Clinical Vet Advisor – Dogs and Cats, 3rd ed. Bassert, Beal and Samples, McCurnin’s Clinical Textbook for Veterinary Technicians, 9thed, pp. 417. Image courtesy of enableuser.
