VPAR 131 Lecture Notes: The Malaria Organisms and Relatives PDF

VPAR 131 Lecture Notes 5/10/24 VPAR 131 Veterinary Entomology and Protozoology The Malaria Organisms and R...

VPAR 131 Lecture Notes 5/10/24 VPAR 131 Veterinary Entomology and Protozoology The Malaria Organisms and Relatives 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 the class, the students should be able to: 1. describe the biological features of malaria parasites, 2. discuss the life cycle of Plasmodium spp. and its difference with Haemoproteus and Leukocytozoon spp., 3. describe the pathological features of various malariae, and 4. discuss diagnosis, treatment and control Prepared by Dr. RL Galay 1 VPAR 131 Lecture Notes 5/10/24 Malaria “Mal’aria”- Italian spoiled air The most important mosquito-borne parasitic disease reported in 85 countries. In 2022, there were 249 M reported human cases with 608,000 deaths worldwide (World Health Organization). For 2,500 years, this disease was attributed to miasmas rising from swamps. Charles Louis Alphonse Laveran was the first to discover the presence of malarial parasites in erythrocytes. Ronald Ross was the first to implicate the role of mosquitoes in the transmission of malaria parasites. Bignami and Grassi proved that mosquitoes transmit malaria to humans. Family Plasmodiidae Life cycle is similar to coccidia, but it is shared by a vertebrate and invertebrate host. Asexual development occurs in vertebrate hosts while sexual development occurs in blood-sucking invertebrates. Gamonts develop independently. Microgamont produces a moderate number of flagellate gametes. Prepared by Dr. RL Galay 2 VPAR 131 Lecture Notes 5/10/24 Family Plasmodiidae Zygote is motile. Sporocysts are absent. Sporozoites occur inside oocyts. Hemozoin (Hz) pigment may be formed from the hemoglobin of invaded Oocyst with sporozoites erythrocytes. Previously, the three genera of veterinary and medical importance, Plasmodium, Haemoproteus, and Leukocytozoon, belong to separate families, but recently they have been grouped under a single family. Plasmodium spp. Causative agent of malaria in humans, mammals, reptiles, and birds. Schizogony occurs in erythrocytes and also in various tissues (cryptozoites). Gamonts occur in erythrocytes. Anopheles mosquitoes are vectors of malaria in mammals while culicine mosquitoes transmit avian malaria. Prepared by Dr. RL Galay 3 VPAR 131 Lecture Notes 5/10/24 Plasmodium spp: Life Cycle Inoculation of sporozoites Exoerythrocytic schizogony Sporogony Erythrocytic schizogony Syngamy Gametogony White et al., 2014 Plasmodium spp. of mammals Plasmodium spp. of humans: P. falciparum, P. vivax, P. knowlesi, P. malariae, and P. ovale. Plasmodium spp. of non-human primates: P. schwetzi, P. reichenowi, P. eylesi, P. coatneyi, P. cynomolgi, P. gondori, P. simium, P. inui, and P. brasilianum Plasmodium spp. of rodents: P. berghei, P. vickei, and P. chabaudi Plasmodium spp. of ungulates: P. bubalis, P. odocoilei Classification of based on length of schizogony cycle: – Quotidian- only 1 day; P. knowlesi – Tertian- 2 days; P. falciparum, P. ovale, P. vivax, P. schwetzi, P. reichenowi, P. eylesi, P. coatneyi, P. cynomolgi, P. gondori, P. simium – Quartan- 3 days; P. malariae, and P. inui, and P. brasilianum Prepared by Dr. RL Galay 4 VPAR 131 Lecture Notes 5/10/24 Plasmodium spp. of birds Over 30 species are identified. Exoerythocytic schizonts do not occur in the liver. After inoculation, pre- erythrocytic schizonts are merozoites found in macrophages and fibroblasts near the inoculation site. Merozoites of P. gallinaceum, P. relictum and P. canthemerium enter endothelial cells, while those of P. elongatum and P. vaughani trophozoite enter cells of hemopoietic system and form exoerythrocytic schizonts. Plasmodium spp. of birds Schizogony cycle Ø 24 hours: P. canthemerium, P. juxtanucleare, P. durae, P. lophurae, P. rouxi, and P. vaughani Ø 36 hours: P. gallinaceum and P. relictum Ø 48 hours: P. circumflexum Two groups based on shape of gamonts: ØRound or irregular, displaces the the nucleus: P. gallinaceum, P. canthemerium, P. juxtanucleare, P. relictum, and P. griffithsi. ØElongate, usually does not displace the nucleus : P. circumflexum, P. durae, P. elongatum, P. rouxi, P. fallax, P. hexamerium, P. lophurae, P. polare, and P. vaughani Prepared by Dr. RL Galay 5 VPAR 131 Lecture Notes 5/10/24 Plasmodium spp. of birds Plasmodium spp. of reptiles Most commonly reported in lizards, occasionally in snakes. At least 101 species are reported to infect reptiles. Three species were reportedly found in Draco volans from Palawan: Plasmodium draconis, P. vastator, and P. volans. One species, P. auffenbergi was found in Varanus grayi from Luzon Various stages of a Plasmodium species from a lizard (Tropidurus) from Brazil (Cordoba et al., 2021). Prepared by Dr. RL Galay 6 VPAR 131 Lecture Notes 5/10/24 Pathology of Human Malaria Human malaria is characterized by paroxysm, which begins with severe chill. P. vivax, the cause of benign tertian malaria, is the commonest and most widely distributed malarial infection in the world. P. falciparum, the cause of malignant tertian malaria, is the most pathogenic in humans due to its cerebral form. Another complication is blackwater fever, characterized by fever, jaundice and hemoglobinuria. Pathology of Avian Malaria Among the pathogenic Plasmodium of birds are P. canthemerium (canaries), P. gallinaceum (domestic chickens), P. relictum (pigeons), and P. juxtanucleare (chickens and turkeys). Enlarged Splenomegaly and anemia spleen are common findings. Brown- tinged skin and darkening of the viscera may be observed due to pigment deposition. P. galinaceum and P. juxtanucleare may cause mortality as high as 90% in chickens. Prepared by Dr. RL Galay 7 VPAR 131 Lecture Notes 5/10/24 Pathology of Avian Malaria Experimental studies on P. gallinaceum showed that it can cause depression, fever, anorexia, reduced weight gain, poor feed conversion, anemia, and green feces. Lethargy, pale comb, diarrhea, and partial or total paralysis may be observed in acute infection. Mortality was observed between 5-10 days post-inoculation. Hepatomegaly and increased gall bladder volume were observed in P. gallinaceum-infected chickens. A separate study reported abnormalities in the brain, including brain edema, inflammatory infiltrates, congested capillaries. Plasmodium juxtanucleare can also cause CNS signs due to exoerythrocytic forms that damage the endothelial cells of the brain. Hepatocystis Infects monkeys, fruit bats, and squirrels. Midges (Culicoides) are the arthropod vectors. Life cycle resembles that of Plasmodium, except schizogony in the liver produces visible cysts (merocyst). Hemozoin pigment is deposited in the liver and spleen. Species: Hepatocystis kochi, H. semnopitheci, H. Ejotre et al., 2021 taiwanensis, H. bouillezi, H. cercopitheci, and H. foleyi. Prepared by Dr. RL Galay 8 VPAR 131 Lecture Notes 5/10/24 Haemoproteus spp. More than 120 species have been identified. Species affecting domestic birds: Ø H. columbae- pigeon Ø H. meleagridis- turkey Ø H. nettionis- duck, goose, swan Vectors are hippoboscid flies, midges (Culicoides spp.), or Chrysops spp. Macrogametocytes Life cycle is similar to that of Plasmodium except that schizogony occurs in endothelial cells of blood vessels Gametocytes occur in erythrocytes with a halter-shape apperance surrounding the nucleus. Microgametocytes Hemozoin is also present. Leucocytozoon spp. Schizogony occurs in the parenchyma of liver, heart, kidney or other organs. Macrogametes and microgametes occur in blood cells (erythrocytes, lymphocytes, monocytes). Hemozoin is not formed. Vectors are black flies (Simulium) or biting midges (Culicoides). Common species: – L. simondi- young ducks and geese. – L. caulleryi- domestic chickens – L. smithi- turkeys Prepared by Dr. RL Galay 9 VPAR 131 Lecture Notes 5/10/24 Haemoproteus & Leukocytozoon: Pathogenesis H. columbae is considered lowly pathogenic, but heavy mortality has been noted in pigeon nestlings. Clinical signs are anorexia and anemia. Necropsy findings include enlarged and dark liver and spleen. L. caulleryi is highly pathogenic in chickens, causing anemia, Ducklings infected with L. hemorrhages in internal organs, simondi can be listless, splenic enlargement, and white anorexic, rapidly breathes, spots in heart muscle; and may show nervous megaloschizonts appear in the derangements prior to death. kidney, lung, and heart,, not in liver. Diagnosis of Malaria Infections Microscopic examination of blood smear stained with Romanowsky stains. Antibody-based detection tests are available for human malaria detection, which is rapid, specific, and more sensitive. New-generation tests based on detection of plasmodium lactate dehydrogenase. Prepared by Dr. RL Galay 10 VPAR 131 Lecture Notes 5/10/24 Treatment and Control of Malaria Quinine is the first drug used for treatment of malaria in humans. Preceding drugs include quinacrine, chloroquine, primaquine, amodiaquine, and pyrimethamine. In highly endemic areas, chemoprophylaxis with atovaquone–proguanil, doxycycline, primaquine, or mefloquine is recommended. Vaccines against sporozoites have been developed. One vaccine utilizes radiation attenuated P. falciparum sporozites (PfSPZ). Presentation of Dr. Thomas L. Richie in International Congress of Parasitology last August, 2014 in Mexico Prepared by Dr. RL Galay 11 VPAR 131 Lecture Notes 5/10/24 Vaccines against human malaria El-Moamly and El-Sweify, 2023 Treatment and Control of Malaria For Plasmodium infection in poultry, chloroquine (intramuscular for 5 days or orally in water for 1 day), quinacrine (intramuscular for 5 days), primaquine (orally for 1 day), and trimethoprim-sulfonamides (intramuscular) can be used. Pyrimethamine alone can be used for treatment of leukocytozoonosis, while pyrimethamine + sulfadimethoxine can be used for prophylaxis. Prevention: preventing mosquito bite using repellents and putting up screens; control of vector mosquitoes and other insects. Prepared by Dr. RL Galay 12 VPAR 131 Lecture Notes 5/10/24 References Bowman. Georgi’s Parasitology for Veterinarians. 10th ed. 2014. Córdoba OH et al. Plasmodium ouropretensis, n. sp., a new case of non- erythrocytic species within lizard malaria parasites. Parasitology. 2021. Deplazes et al. Parasitology in Veterinary Medicine. 2016. El-Moamly & El-Sweify. Malaria vaccines: the 60-year journey of hope and final success—lessons learned and future prospects. Trop Med Health. 2023. Jacobs et al., Principles of Veterinary Parasitology. 2016. Kauffmann. Parasitic Infections of Domestic Animals. 1996. Macchi et al. Pathogenic action of Plasmodium gallinaceum in chickens: brain histology and nitric oxide production by blood monocyte-derived macrophages. Vet Parasitol. 2010 Tostes et al., Plasmodium spp. and Haemoproteus spp. infection in birds of the Brazilian Atlantic Forest detected by microscopy and polymerase chain reaction. Pesq Vet Bras. 2015. Valkiūnas and Iezhova. Exo-erythrocytic development of avian malaria and related haemosporidian parasites. Malar J. 2017. White et a., Malaria. The Lancet. 2014. Prepared by Dr. RL Galay 13