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Hepatozoon sciuri (Coles, 1914) is reported from gray squirrels ( Sciurus carolinensis ) in Washington, D.C. and Maryland. Blood smears stained with Giemsa's stain revealed a parasitemia in 16 to 71% of the squirrels examined. A technique for laking the red cells and concentrating the white cells in blood samples demonstrated this protozoon to be present in every squirrel so tested.
Two new species of Microsporidea, Plistophora salmonae from steelhead and rainbow trout (Salmo gairdntri) and Plistophora crpedianar from gizzard shad ( Dorosoma cepedianum) are described. Schizonts to spores of P. cepedianae were found at one time within the same cyst, while only sporonts and spores of P. salmonae were found within the cyst. An illustrated synopsis of the known Microsporidea of freshwater and euryhaline fishes is given.
Eimeria aurati n. sp. is described from the intestine of the goldfish, Carassius auratus , from Pennsylvania, U.S.A. Oocysts were very numerous in long, whitish, opaque fecal casts. They were 16 to 24 by 14 to 17 μ (mean, 20.1 by 16.3) and were non-sporulated when passed but sporulated 2 to 5 days later.
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In the anemia which accompanies infection by Leucocytozoon simondi in Pekin ducks there was a far greater loss of erythrocytes than could be accounted for as a result of direct physical rupture by the parasite. Erythrocyte loss began at the same time the 1st parasites appeared in the blood and was severest just prior to maximum parasitemia. Blood replacement and parasite loss occurred simultaneously. Examination of the spleen and bone marrow revealed that erythrophagocytosis was not the cause of anemia as reported for infections of Plasmodium, Babesia and Anaplasma . An anti-erythrocyte (A-E) factor was found in the serum of acutely infected ducks which agglutinated and hemolyzed normal untreated duck erythrocytes as well as infected cells. This A-E factor appeared when the 1st red cell loss was detected and reached its maximum titer just prior to the greatest red cell loss. Titers of the A-E factor were determined using normal uninfected erythrocytes at temperatures between 4 and 42 C. Cells agglutinated below 25 C and hemolyzed at 37 and 42 C. These results indicated that the A-E factor could be responsible for loss of cells other than those which were infected and could thus produce an excess loss of red cells.
Nonimmune homing pigeons Columba livia were infected with the Jones' Barn strain of Trichomonas gallinae and subsequently transfused with plasma from acute or chronically infected pigeons harboring one of 3 different strains of T. gallinae. The transfusions were either a single 2 ml dose given one day after inoculation or three 1 ml doses given 0, 5, and 10 days after inoculation. Plasma from pigeons harboring any of the 3 strains was capable of passively immunizing nonimmune birds. All birds which were immunized with plasma from infected pigeons survived until killed at the end of the test period and no visceral lesions were found on necropsy but trichomonads were present in the oropharynx. All controls (untreated or transfused with normal plasma) died of visceral trichomoniasis. Immune plasma produced some lysis of trichomonads in vitro, and inhibition of motility and vacuolization occurred in some of the non-lysed organisms. The overall lytic activity in vitro affected less than 10% of the suspended trichomonads.
An intracellular protozoon was discovered in the epithelium of young rainbow trout ( Salmo gairdneri ) exposed for as short a time as 1 hr to water known to contain infective stages of Myxosoma cerebralis. Light- and electron-microscopic examination of this tissue revealed what appeared to be a proliferative stage (presumptive schizont) of a sporozoon; other possible stages in the life cycle were also observed. The relationship of this unidentified protozoon to M. cerebralis remains unresolved.
Trophozoites and other pre-spore stages of the myxosporidan Myxosoma cerebralis were taken from infected rainbow trout ( Salmo gairdneri ) and cultured in vitro. Cultures eventually yielded mature spores capable of discharging their polar capsules. This is the first report of culture of a myxosporidan.
Studies of the life cycle of Myxosoma cerebralis showed that development of infectivity did not occur endogenously but that the spore “aging” process required participation of an aquatic tubificid oligochaete. Data suggestive of such involvement were derived from trials in which spores were “aged” in an array of inert, sterilized, pasteurized, or natural aquatic substrates and from examination of aquatic soils from trout hatcheries in which whirling disease was epizootic. The role of the aquatic oligochaete was confirmed two ways. First, signs of whirling disease developed, and M. cerebralis spores were produced in young rainbow trout ( Salmo gairdneri ) that had been fed oligochaetes harvested from pond soil taken from two hatcheries where whirling disease was epizootic. Second, when containers of pasteurized soil were populated with four genera of oligochaetes– Aeolosoma, Dero, Stylaria , or Tubifex – from a biological supply house, or with tubificid worms from trout hatcheries free of whirling disease, and then seeded with M. cerebralis spores and “aged” for 4 months, whirling disease occurred only in trout held with Tubifex and with hatchery tubificids.
Two new species of Myxozoa from the brain of the green knife fish Eigemannia virescens are described: Myxobolus inaequus sp. n. has an unusually large spore body and extremely unequal polar capsules, and Henneguya theca sp. n. has an attenuated spore encased in a sheath not previously described in other Myxozoa. Only spores of the two species were observed, and infections caused no obvious pathological changes in the brain.