The Coccidia. Heteroxenous Species.pdf

VPAR 131 Lecture Notes 5/9/24 VPAR 131 Veterinary Entomology and Protozoology The Coccidia: Heteroxenous Cyst-...

VPAR 131 Lecture Notes 5/9/24 VPAR 131 Veterinary Entomology and Protozoology The Coccidia: Heteroxenous Cyst-forming species Remil L. Galay, DVM, DVSc Associate Professor This presentation is for instructional purposes only, for the course in which this is delivered. The use and distribution of this presentation without written consent from the lecturer is strictly prohibited. Any reproduction and/or communication of the material by you may be subject to copyright infringement and the copyright owners have the right to take legal action against such infringement. LECTURE OBJECTIVES At the end of this lecture, students should be able to: 1. describe the general biological features of cyst-forming coccidia, 2. discuss the life cycle of Cystoisospora, Sarcocystis spp., Toxoplasma gondii, and Neospora caninum, 3. describe the pathological features 4. discuss diagnosis, treatment and control 5. describe some aspects of Besnoitia and Hammondia. Prepared by Dr. RL Galay 1 VPAR 131 Lecture Notes 5/9/24 LECTURE OUTLINE ØGeneral features of Family Sarcocystidae ØCystoisospora ØSarcocystis ØToxoplasma ØNeospora ØBesnoitia besnoiti ØHammondia Family Sarcocystidae Differs from Eimeriidae in that their life cycle is heteroxenous, i.e. they require one type of host for the sexual reproduction and another for asexual reproduction. All hosts are vertebrates. Final hosts (FH) are carnivores, while and intermediate hosts (IH) are mostly prey animals. Oocysts may sporulate within the FH or in the environment. Prepared by Dr. RL Galay 2 VPAR 131 Lecture Notes 5/9/24 Family Sarcocystidae Each sporulated oocyst contain two sporocysts with four sporozoites each. Oocysts are produced and sporulate in the intestinal cells of the FH, Sporulated Oocyst while the asexual stages (tachyzoites and bradyzoites) are in the tissues of the IH. Members include Cystoisospora, Toxoplasma, Sarcocystis, Tachyzoites Bradyzoites Neospora, Besnoitia, and Hammondia Cystoisospora Formerly under Isospora but reclassified into a separate genus. Stieda bodies absent in the sporocyst. Dogs and cats can become infected by ingesting sporulated oocysts from the environment or through predation. In prey animals (e.g., rodents and birds), sporozoites can infect tissues and encyst Prepared by Dr. RL Galay 3 VPAR 131 Lecture Notes 5/9/24 Cystoisospora Species affecting dogs: Cystoisospora canis, C. ohioensis, C. burrowsi and C. neorivolta. Species affecting cats: C. felis and C. rivolta Infection is usually subclinical. Young animals are more susceptible to infection. Puppies and kittens may get infected between three and eight weeks of age. The majority of clinical cases are diagnosed in animals less than four months old. Cystoisosporosis can cause diarrhea, which may contain blood in severe cases. Most develop acquired immunity. Diagnosis: fecalysis for oocysts; must allow sporulation for differentiation with Eimeria. Treatment: Toltrazuril and diclazuril are the drugs of choice. Oral sulfadimethoxine and trimethoprim-sulfonamide may also be used. Sarcocystis Sarcocysts containing bradyzoites form in striated and cardiac muscles, occasionally the brain of the IH, and are the infective form for the FH. Two types of cysts: macrocyst and microcyst. Metrocytes, rapidly dividing Oocyst forms that dominate immature cysts, are present. Oocysts sporulate within FH like carnivores and man. Sporulated oocysts or sporocysts are passed in the feces. IH, e.g. ruminants, pig, horse, rodents are infected by Sarcocyst ingesting sporocysts. Prepared by Dr. RL Galay 4 VPAR 131 Lecture Notes 5/9/24 Sarcocystis species in domestic animals Dubey and Lindsay, 2006 Sarcocystis: Life Cycle FH gets infected by predation Merozoites form sarcocyst in muscles. Schizogony occurs in endothelial cells in small blood vessels. Sexual reproduction occurs in intestine of FH forming oocysts Sporocysts are swallowed by the IH Prepared by Dr. RL Galay 5 VPAR 131 Lecture Notes 5/9/24 Sarcocystis: Pathogenesis Most Sarcocystis spp. are considered of low pathogenecity. Infection in FH is usually non-pathogenic. Pathogenic effects in the IH are due to tachyzoites and merozoites in endothelial cells. Intact sarcocyts do not appear pathogenic but may contain endotoxin known as sarcocystin. Sarcocystis of cattle S. cruzi (bovicanis) is the most pathogenic species. Clinical signs include protracted fever, anemia, lymphadenopathy, anorexia, diarrhea, hypersalivation, weakness, hair loss around the eyes, and tail twitch. Reduced milk yield, abortion, and placentitis may be observed in cows. Heavy infection in calves may cause petechial hemorrhages and generalized lymphadenopathy. Prepared by Dr. RL Galay 6 VPAR 131 Lecture Notes 5/9/24 Sarcocystis of sheep S. tenella (=S. ovicanis) is highly pathogenic for lambs. S. gigantea produces rounded macroscopic sarcocysts in the esophagus and tongue. Beveridge and Emery, 2015 Clinical signs include fever, inappetence, anemia. Mild infection (