Abstract
Image 1
A. Babesia bovis
Babesia spp. are 1 to 2 µm intraerythrocytic protozoal parasites transmitted by ticks, transplacentally, or via blood transfusions. The Wright or Wright-Giemsa stains best demonstrate the organisms. Intravascular and extravascular hemolysis is a result of direct damage by the parasite and a cause of secondary immune-mediated hemolytic anemia. Animals dying due to acute disease have splenomegaly, jaundice, hemoglobinuria, swollen hemoglobin-stained kidneys, cardiac hemorrhages, and generalized gray matter congestion (“cerebral flush,” Image 1). Meningomelanosis (incidental finding) is also present in the rostral part of the illustrated brain (Image 1). Theileria taurotragi infects lymphocytes, Trypanosoma theileri are extracellular flagellated trypomastigotes, and Ehrlichia ruminantium infects endothelial cells.
Additional reading: Boes KM, Durham AC. Bone marrow, blood cells, and lymphatic system. In: Zachary JF, ed. Pathologic Basis of Veterinary Disease. 6th ed. St. Louis, MO: Saunders Elsevier; 2017:748.
Contributor: Pompei Bolfa, Ross University School of Veterinary Medicine, St. Kitts and Nevis
Image 2
C. Platynosomum illiciens
The feline liver fluke, Platynosomum illiciens (previously Platynosomum fastosum), is prevalent in the tropics and subtropics. Cats acquire the parasite by eating infected paratenic hosts, lizards (“lizard poisoning”). Clinical signs are rare and include icterus, cirrhosis, distended abdomen, emaciation, lethargy, diarrhea, vomiting, and sometimes death. Adult flukes inhabit the bile ducts (Image 2) but can move into the gallbladder and cause chronic cholecystitis, lymphoplasmacytic cholangitis, cholangiectasis, and fibrosing cholangiohepatitis. Trematodes have no body cavity, are hermaphroditic, and have yellow-brown thick-shelled eggs (Image 2). Dicrocoelium dendriticum inhabits bile ducts of ruminants, horses, pigs, dogs, rabbits, rodents, and humans. Athesmia foxi infects monkeys, and Eurytrema procyonis affects the pancreas of raccoons.
Additional reading: Pinto HA, Melo AL, Mati VLT. Platynosomum illiciens. Trends Parasitol. 2022;
Contributor: Pompei Bolfa, Ross University School of Veterinary Medicine, St. Kitts and Nevis
Image 3
D. Aelurostrongylus abstrusus
Pulmonary aelurostrongyliasis is a common parasitic disease of cats around the world. The indirect life cycle of Aelurostrongylus abstrusus includes domestic and wild felids as definitive hosts, terrestrial molluscs as intermediate hosts, and small vertebrates as paratenic hosts. Lesions in feline lungs are the result of egg hatching, larval development, and migration. Although infected cats are usually asymptomatic, heavy infections manifest as anorexia, respiratory signs, and death. White to yellow, firm, slightly raised nodules throughout the lung can be seen grossly. These nodules are histologically composed of eosinophilic and granulomatous pneumonia with eggs, larvae (Image 3), and fewer adult worms.
Additional reading: Caswell JL, Williams KJ. Respiratory system. In: Maxie MG, ed. Jubb, Kennedy and Palmer’s Pathology of Domestic Animals (Vol. 2). 6th ed. St. Louis, MO: Elsevier; 2016:590–591.
Contributor: Igor R. Santos, Universidade Federal do Rio Grande do Sul, Brazil
Image 4
D. Haemoproteus sp. and Leucocytozoon sp.
Avian hemoparasites can occur singly or in mixed infections, which mainly occur in wild birds. Haemoproteus and Leucocytozoon have low pathogenicity, but in young or immunosuppressed birds, they can cause anorexia, depression, leukocytosis, and hemolytic anemia. Image 4 shows two ring-shaped young gametocytes (arrowhead) and a typical mature macrogametocyte (asterisk) of Haemoproteus, which surrounds more than half of the erythrocyte nucleus without displacing it. In contrast, Plasmodium, the cause of avian malaria, appears as ring-shaped gametocytes that decentralize the erythrocyte nucleus, and their schizogony occurs in the peripheral circulation. Both hemoparasites have refractile iron pigment granules, unlike the larger dark purple Leucocytozoon macrogametocytes, which distort and enlarge the host cell into a distended aberrant shape (arrow).
Additional reading: Campbell TW. Exotic Animal Hematology and Cytology. 4th ed. Hoboken. NJ: Wiley-Blackwell; 2015:37–224.
Contributor: Filipe Fontes Pinto. Unit for Multidisciplinary Research in Biomedicine, ICBAS-School of Medicine and Biomedical Sciences, University of Porto, Porto, Portugal
Veterinary Pathology invites submission of exceptional gross or microscopic images for consideration as an Image Challenge, along with a multiple-choice question and answer. For details, see the Instructions to Authors on the journal website.