Biology 625
ANIMAL PARASITOLOGY
Fall semester lecture note outline

Updated: 24 September 1999

General characteristics of Adeleorinids

1. Syzygy present, although gamonts are distinctly anisogamous and termed macrogamonts (female gamonts) and microgamonts (male gametes)
2. Microgamonts generally produce 1-4 microgametes
3. Gamonts of many species motile prior to maturation into gametes
4. Fertilization and sporogony usually within invertebrate definitive host
5. Merogony by binary fission or binary fission, often within vertebrate host
6. Many heteroxenous, and some homoxenous members, within this taxon
7. Seven named families, although only a few important here
   1. Adeleidae (you will not be tested over this taxon)
      1. monoxenous
      2. in invertebrates; reports in vertebrates pseudoparasitism
      3. often polysporic
      4. about nine genera, including Adelea, Adelina, Klossia often distinguished by number of sporocysts within oocysts and sporozoites with sporocysts
   2. Dactylosomatidae (you will not be tested over this taxon)
      1. heteroxenous; leeches definitive hosts; poikilotherm vertebrates intermediate host
      2. meronts, merozoites, and gamonts small in erythrocytes of vertebrates
      3. genus Dactylosoma with 6-16 merozoites per meront and arising by exogenous budding; genus Babesiosoma with 4 merozoites arranged as cruciform shape in meront
   3. Haemogregarinidae
      1. heteroxenous
      2. gamonts within erthrocytes and/or other blood cells
      3. most with merogony in erythrocytes of vertebrate host
      4. sporozoites excyst within invertebrate host, undergo merogony, and merozoites transmitted by bite of leech vector
      5. large numbers of species have been placed in the genus Haemogregarina. However, recent evidence suggests only those species utilizing a leech definitive host may truly belong in this genus (1996, J Parasitol 82: 565-585)
      6. three genera; Haemogregarina spp. having oocysts with 8 sporozoites; genus Cyrilia infecting fish and leeches and with oocysts with 16 sporozoites; Desseria spp. in piscine and leech hosts without intraerythrocytic merogony
   4. Hepatozoidae
      1. heteroxenous
      2. gamonts within erythrocytes and/or leukocytes of amphibia, reptiles, birds, or mammals
      3. merogony in vertebrate host
      4. large, polysporic oocysts with distinct wall form within tissues of invertebrate definitive host. Sporocysts with 4-more sporozoites each. Transmission to vertebrate by ingestion of invertebrate (i.e. mosquitos and other dipterans, bugs, mites, and ticks; perhaps leeches in a few cases).
      5. some vertebrate host species harbor dormant monozoic or dizoic cystozoites in tissue cysts, especially in the lungs (1972, Z Parasitenkd 38: 250-270; 1973, Ann Parasit Hum Comp 48: 11-21; 1990, J Parasitol 76: 257-259). In these cases, the cysts may be transferred to a third (vertebrate) host that is involved in the life-cycle (i.e. paratenic-like host)
      6. genus Hepatozoon
   5. Karyolysidae (you will not be tested over this taxon)
      1. heteroxenous
      2. merogony in endothelial cells, and sometimes erythrocytes, of reptiles and amphbia. Gamonts in erythrocytes.
      3. syzygy and sporogony within acari (tick or mite), followed by excystation and sporozoites initiating merogony. Merozoites ingested along with mites or ticks.
      4. genus Karyolysis (numerous species; normally mite/lizard life- cycles) can be transmitted transovarianly whereas Hemolivia (1 species, anuran/tick life-cycle) cannot
   6. Klossiellidae (you will not be tested over this taxon)
      1. monoxenous
      2. gamogony and sporogony in vertebrate kidney; predominately mammals (i.e. horses, bats, marsupials)
      3. produce polysporic thin-walled oocysts which rupture releasing free sporocysts in the urine
      4. single genus Klossiella
   7. Legerellidae (you will not be tested over this taxon)
      1. monoxenous
      2. variable numbers of naked sporozoites (i.e. no sporocysts) within oocysts
      3. most typically infecting Malpighian tubules of invertebrates
      4. one genus Legerella

Haemogregarina balli (Haemogregarinidae)

1. merozoites in salivary glands of leeches, Placobdella ornata, P. parasitica
2. enters wound of common snapping turtles, Chelydra serpentina when leech bites
3. merogony in turtle
   1. immature meronts found in red blood cells
   2. mature meronts with 6-8 merozoites sequester in liver
   3. mature meronts with 13-25 merozoites sequester in liver, lung, spleen
4. last generation merozoites form gamonts, which are found within erythrocytes; morphogical differences between macrogamont and microgamont
5. blood ingested by leech
6. gamonts released; undergo syzygy; mature (ingested meronts degenerate)
7. microgamont produces 4 microgamets; one microgamete fertilizes macrogamete in gut of leech
8. zygote; oocyst forms and sporulation forming 8 sporozoites
9. excystation 1
10. enter endothelial cells, especially of circulatory system
11. sporozoites penetrate cells; undergo slow, long term merogony over a period of months to form merozoites
12. merozoites migrate and accumulate in salivary glands
13. 1976, J Protozool 23: 294-301; 1990, J Protozool 37: 511-520; 1991, J Parasitol 77: 426-436.
14. similar species
    1. Haemogregarina stepanowi in european turtles (Emys orbicularis) and european leeches (Placobdella costata)
    2. Many species may eventually be found to represent Hepatozoon spp. and most members of the genus have been transferred (1995, J Protozool 42: 116-125; 1996, J Parasitol 82: 565-585)

Hepatozoon (Haemogregarina) catesbianae (Hepatozoidae)

1. in bullfrogs (Rana catesbeiana) and mosquitos (Culex territans) (1995, J Parasitol 81: 212-222)
2. meronts in liver; numerous merozoites per meront; number of asexual generations as yet unknown; individual merozoites sometimes found in erythrocytes prior to sequesteration
3. gamonts in red blood cells
4. ingested by mosquitos
5. enter cells of the Malpighian tubules
6. syzygy; fertilization
7. sporulation with polysporic oocysts and 4 sporozoites per sporocyst
8. mosquito is ingested by frogs and inititates new infection
9. similar species
   1. Hepatozoon canis in canids (Canis spp.)
   2. Hepatozoon crotali in rattlesnakes (Crotalus spp.)
   3. Hepatozoon griseisciuri in grey squirrels (Sciurus carolinensis)
   4. Hepatozoon muris in rats (Rattus spp.) and mites (Laelaps echidninus)
   5. Hepatozoon rarefaciens in Indigo snakes (Drymarchon corais) and mosquitos (several different genera)
   6. Hepatozoon thamnophis in garter snakes (Thamnophis spp.)
   7. Some vertebrates require an intermediate (vertebrate) prey host harboring dormant monozoic or dizoic cysts in order to become infected. It is thought that these intermediate hosts undergo the same parasite development (i.e. merogony and gamogony) as the predator vertebrate host
      1. Hepatozoon sipedon in water snakes (Nerodia spp.) cannot directly infect snakes when the snakes are fed mosquitos harboring the sporulated oocysts; utilizes frogs possessing dizoic hepatic cysts as the mode of infection.
      2. Hepatozoon domerguei in snakes and requires a lizard (Oplurus sebae) with dizoic lung cysts to become infected. However, the life-cycle can occur between moquitos and lizards without the need for snakes