Number Of Merozoites Research Articles

A New Species of Avian Plasmodium

SYNOPSIS. A new species of avian malaria parasite is described, for which the name Plasmodium formosanum is proposed. It was observed in the blood of Arboriphila crudigularis, the Formosan hill partridge; other bird species in which it may occur remain unknown, as do the mosquito vectors. It produces very broad, elongate gametocytes, the macrogametocyte usually exhibiting a very large vacuole. The usual number of merozoites is eight. The host cell nucleus typically is not displaced, except laterally by the sexual forms. Only the stages occurring in the blood have yet been seen.

Temperature studies on chicks infected with Plasmodium gallinaceum (Brumpt, 1935) including some effects of cooling host and parasite

It was confirmed that P. gallinaceum had a 36-hour period of development and was relatively synchronous. The period remained 36 hours even when a bird was infected with sporozoites three times, at consecutive 12 hours intervals. The rectal temperatures of young chicks showed an increase during the first two weeks of life. Fluctuations of temperature from day to day were generally about ±0.2 ° C. A 24-hour temperature cycle was found which was related to the birds' activity rhythm. The temperatures of infected birds were not affected by any stage of the parasites' 36-hour growth cycle, but abnormal temperatures occurred at the peak of parasitaemia. The degree of temperature abnormality was directly related to the severity of the infection. Infected birds were cooled to approximately 30 ° C and were revived after about six hours. Cooling delayed the growth of the parasite by causing the period of development to extend beyond the usual 36 hours. This extension was more marked when trophozoites predominated in the blood during the cooled period. There was no detectable difference between cooled birds and controls in the rate of parasitic increase, the morphology of the parasite, or the number of merozoites per schizont. Gametocytes from cooled birds infected mosquitoes and exoerythrocytic parasites were found in cooled birds 22 days after infection.

Changes in infectiousness of malarial gametocytes. II. Analysis of the possible causative factors

The former paper (Huff and Marchbank, 1955) clearly indicated a general pattern among seven host-parasite combinations involving avian malarial parasites; this pattern being a rapid and continuing fall in the infectivity of gametocytes for mosquitoes during the course of infection in the bird. An analysis has been made in the present paper of the factors which might contribute to this change in infectivity of gametocytes. The aim has been the testing of two hypotheses to account for the decrease in this infectivity, namely (1) that it was due to a deficiency in the host which developed as the infection progressed, or (2) that an immune mechanism was responsible for the decrease. The following substances were administered to birds during the course of their infections: uninfected whole blood, coenzyme A, ferrous sulfate, sodium glutathione, calcium pantothenate, and sucrose. These substances did not enhance the infectivity of the gametocytes. In two experiments the hosts were bled daily during the course of their infections. No appreciable differences in oocysts numbers or infectivity values (oocyst-gametocyte ratios) were observed between the bled birds and the controls. Two experiments were performed testing whether mixed infections would yield evidence of a greater depleting effect. The results were not clearly conclusive but were suggestive that at least the principal cause of decrease in infectivity of the gametocytes was not a depleting effect. In one experiment in which blood infected with P. gallinaceum was transfused to a naturally immune host (duck) there was an appreciable increase in infectivity values of the mosquitoes. Two attempts to demonstrate effects on the gametocytes by the passive transfer of serum from hyperimmunized birds gave negative results. Two transfusion experiments were carried out in which infected blood was transmitted to birds with acquired immunity. No detectable change was observed in infectivity of gametocytes in one of these, while there were indications of a rapid fall in their infectivity in the second. Four experiments (three with P. gallinaceum in chickens and one with P. fallax in turkeys) testing the effect of immunization with killed parasites prior to the infecting inoculation uniformly indicated an early, more rapid fall in infectivity of gametocytes in the immunized than in the control animals. The results of all experiments can better be explained on the hypothesis that active immunity is the cause of decreasing infectivity of gametocytes than one in which this effect is assumed to result from a depletion effect of infection on the host. As in the former paper the lowering in mean numbers of merozoites produced by segmenters observed by other investigators during the crisis was not observed. However, significant differences were observed between the mean numbers of merozoites of infections in birds on adequate diets and those deficient in pantothenic acid.

The Endogenous Development of Eimeria alabamensis Christensen, 1941, an Intranuclear Coccidium of Cattle

SUMMARY. The endogenous development of the life cycle of Eimeria alabamensis Christensen, 1941, occurs in the nucleus of the intestinal cells of cattle. Calves were killed at various intervals after inoculation with infective oöcysts to study the endogenous cycle. Excysted sporozoites were found in the contents or scrapings from the walls of rumen, omasum, small intestine, cecum, and colon. They were found in the cytoplasm of intestinal epithelium at 2 days. Schizonts were found in the nuclei beginning at 2 days, but the number was low by the 8th day. Merozoite numbers usually ranged between 16 and 32. Some host nuclei contained as many as 48 or more, but these appeared to be the result of more than one schizont merging in the same host nucleus. Merozoites were slender, spindle‐shaped bodies while still in the schizont walls, but were short with bluntly rounded tips when found in intracellular spaces and crypts. Gametocytes were found as early as the 4th day. Most of the stages of gametogenesis were limited to the lowest third of the small intestine, but in heavy infections some were also found in the cecum and upper colon. Microgametocytes were multinucleate and were more densely stained than the uninucleate macrogametocytes. The ratio of macrogametocytes to microgametocytes in 100 gametes was 78: 22. Oöcysis with “shells” were found in sections of the lower 20 feet of the ileum on the 6th day, which coincided with the shortest prepatent period reported previously. As many as three schizonts or microgametocytes or four or five macrogametocytes or oöcysts could be found in the same host nucleus. The variations in shape of the oöcysts appeared to be dependent on the number of oöcysts crowded into each nucleus.

A Study of Changes Occurring in Plasmodium lophurae after Three Years of Continuous Existence in Mice

SUMMARY. The characteristics of Plasmodium lophurae infections in mice have been studied for a period of 3 years. The average height of parasitemias increased steadily for several months then leveled off with but minor changes for the remainder of the time. Gametocytes were found during the ninth month after the passages were begun. Comparison of the strain after 3 years in mice with the same species of parasite maintained constantly in chick embryos indicated that the sojourn in the mouse had temporarily disturbed the mean numbers of merozoites produced.

Glucose Consumption of Plasmodium hexamerium

Despite a number of studies by investigators in different parts of the world, our knowledge of the physiology of the malaria parasites is still fragmentary. This is true even of the species of Plasmodium causing human malaria; of most of the others we know little or nothing, although some of those infecting monkeys and birds have been rather intensively studied. Plasmodium hexanerium is still one of the less known species, but it produces good infections in ducklings and therefore lends itself to research of various kinds. It is also representative of a natural subgroup of malaria plasmodia, characterized morphologically by the production of a rather small number of merozoites per segmenter (generally 8 or less), by elongate gametocytes, and by small size. Periodicity of asexual reproduction is not marked in the group, and the infections produced lack (in the natural host species) a sharply marked crisis, and tend to be very chronic. This subgroup has been little studied physiologically, and for this reason Plasmodilum hexamrerium was selected for an investigation of its rate of glucose consumption. Previous studies of this type dealt only with a few of the larger species of plasmodia. MATERIALS AND METHODS The methods employed were essentially those used in two similar studies (Manwell and Feigelson, 1949; Warren and Manwell, 1954) done in this laboratory. White Pekin ducklings, generally not more than a week old, were used as experimental animals. Infections were produced by the inoculation of infected blood into the jugular vein, the infective dose having been taken by intracardial puncture from a donor duckling, in which the parasite count was still rising (to avoid possible

Changes in infectiousness of malarial gametocytes. I. Patterns of oocyst production in seven host-parasite combinations

The infectiousness of gametocytes for mosquitoes during the course of infection in the vertebrate was determined in seven combinations of the following parasites, avian hosts, and mosquitoes: Plasmodium gallinaceum, P. fallax, and P. cathemerium; chicks, pigeons, guinea fowl, turkeys, and canaries; Aedes aegypti, A. albopictus, Culex pipiens, and C. tarsalis. In 22 infections the peak of oocyst production consistently preceded the peak of parasitemia by 1 to 4 days (average 2 days) with the result that there was a precipitate fall in oocyst numbers during a period when the total numbers of parasites—as well as gametocytes—was still increasing. The patterns in change of oocyst numbers during the course of infection was similar in infections with the three species of parasites, except that in P. cathemerium infections in canaries there was a recovery in the ability to produce oocysts three days after the beginning of the decline. In the only instance where the experiment was continued long enough to determine the subsequent happenings, a second peak of oocyst production occurred. In the one experiment where comparisons could be made between the results in two different species of mosquitoes, simultaneous feedings of both C. pipiens and C. tarsalis were made daily during the course of infection of P. cathemerium in a canary. The oocyst counts in C. tarsalis were at all times higher than in C. pipiens and there was a very close parallelism between the counts in the two species of mosquitoes. Infections of P. fallax were studied in pigeons, chicks, guinea fowl and turkeys. Patterns of change in oocyst numbers were comparatively alike in turkeys but very variable in pigeons. The chick was a poor host and the guinea fowl a very good host in respect to the relation between degree of parasitemia and number of oocysts produced. Fairly good infections resulted in mosquitoes fed on guinea fowl even though gametocytes were not seen in the blood smears on 5 of the 8 days they were fed. Oocyst size did not vary with fluctuations in degree of parasitemia or number of oocysts per mosquito. There was, however, some evidence that the size of oocysts was affected by differences in individual avian hosts. No changes in rate of reproduction of asexual stages paralleling the changes in infectiousness of gametocytes were reflected in the mean numbers of merozoites formed during the course of infection.

The infection by Plasmodium lophurae of duck erythrocytes in the chicken embryo.

Certain morphological differences render it possible to recognize duck erythrocytes after introduction into the circulating blood of chick embryos infected with P. lophurae. 4 hours afterward, considerable numbers of merozoites have entered duck erythrocytes, while the parasitemia of the chick itself remains essentially unchanged in degree. By estimating the numbers of potentially invading merozoites from blood films made at the time of introduction of duck cells, it was learned that a relatively constant rate of invasion into duck cells by merozoites was maintained. In counter-distinction there was an ever increasing merozoite death rate in embryos not receiving duck cells concurrent with the increase in numbers of parasites. After the injection into parasitized embryos of duck erythrocytes showing but few parasites, no difference was apparent in the rate of merozoite invasion into the introduced cells and the host cells, respectively; but when the percentage of duck cells was greater, the rate of merozoite penetration diminished to zero. The selective penetration of duck erythrocytes which, under the experimental conditions obtaining, constituted only 30 per cent of the total cell numbers of most, and the inability of the merozoites to move independently, taken together, suggest that the greater susceptibility of the duck erythrocyte may be due to greater numbers of accessible areas on its surface. The decreased susceptibility following parasitization indicates that the presence of the parasite alters the cell in such wise that entry of additional parasites is rendered more difficult.

Plasmodium of a primate of Brazil

A second species of monkey Plasmodium of the New World is described from the howler monkey Alouatta`fusca GEOFFROY, 1812, captured in Itapecirica, Sao Paulo, Brazil. The new species differs from Plasmodium brasilianum GONDER et VON BERENBERG-GOSSLER, 1909 by following characters: 1st. Almost constant presence in the blood cells of granulations of the same type as SCHUFFNER dots. 2nd. Considerable hypertrophy of the parasitised cells. 3rd. Greater number of merozoites after schizogony with an habitual minimum of 16 elements in contrast with the maximum of 16 in Plasmodium brasilianum. 4th. Extreme rarity of band forms. This morphology strongly suggests an infection of the benignan tertian type. To this new species the name of Plasmodium simium, sp.n. is proposed.

The response of blood-inoculated and sporozoite-induced infections of Plasmodium relictum to drugs

1. When sporozoite-induced infections of Plasmodium relictum are treated with atebrin (mepacrine) in doses suppressive to blood-inoculated infections, for periods exceeding that of normal incubation, parasites devoid of pigment appear in the erythrocytes of the peripheral blood. A small proportion of these may develop into schizonts, but the number of merozoites produced is fewer than normal.2. A similar phenomenon occurs when quinine is substituted for atebrin, but the drug appears to be excreted more rapidly so that the inhibitive effect upon growth is less marked.3. When plasmoquine is given in the maximum tolerated dose to birds infected with sporozoites, parasites are not seen in the peripheral blood during treatment, though the infection is not sterilized. With smaller doses parasites, including a few small schizonts, are found in the erythrocytes during treatment.4. Merozoites produced in the erythrocytes during drug treatment are not capable of further multiplication when inoculated into uninfected birds having a similar blood-concentration of drug, so long as treatment continues, though they develop normally when transferred to untreated birds.5. No indication of drug resistance has been observed.6. The possible mechanisms by which blood-inoculated infections are eradicated, or resist eradication, are discussed.We wish to thank Miss Vincent (Mrs Thorpe) and Dr Parr Tate for access to their preliminary unpublished experiments, and the latter for helpful criticism.

Life-Cycle of Plasmodium Relictum Var. Matutinum

Summary and Conclusions 1. Exoerythrocytic schizogony has been looked for in 18 cases of infection with Plasmodium relictum var. matutinum, and demonstrated in 9. It has been found both in blood-induced infections and those resulting from the bites of infected mosquitoes. 2. Exoerythrocytic schizonts in this subspecies present no particular characteristics not seen in other species, except that they often appear vacuolated in stained preparations. Similar vacuoles have been rather frequently seen in the larger erythrocytic forms (particularly schizonts) also, and this is believed to be further evidence that both these types of schizogony are part of the life-cycle of the same parasite. 3. Most of the cases in which exoerythrocytic forms have so far been observed have shown a preponderance of such stages in the brain. The erythrocytic schizonts also appear to show a tendency to localise in the internal organs, especially in the liver. 4. Transmission of this subspecies has been effected by Culex pipiens. 5. Although Plasmodium relictum var. matutinum is in most respects indistinguishable on morphological grounds from other strains of Plasmodium relictum, it presents a clearcut difference with respect to the number of merozoites produced per segmenter. The mean is about sixteen. Physiologically, as already pointed out by others, it is very different.

Periodicity in the Asexual Cycle of Plasmodium Nucleophilum with Additional Notes on This Species

Summary and ConclusionsThe problem of periodicity in the asexual cycle of Plasmodium nucleophilum has been carefully studied in five birds, together with certain other questions, such as the age of the red cell most commonly attacked by the parasite, and the possibility of exoerythrocytic stages in the vertebrate host. The results may be summarized as follows: 1. Periodicity is marked in this species, and the length of the asexual cycle approximates twenty-four hours. There is however much variation in individual birds, and synchronicity is frequently slight. In general, the peak of segmentation occurs between 10 a.m. and 5 p.m. 2. Mature gametocytes may be found at any time during the twenty-four hours. Peaks in gametocyte number tend to follow by a few hours peaks in schizont number, indicating that the time for maturation of the sexual stages is somewhat greater and their length of life longer. It was found that size of the gametocyte, when mature, was somewhat larger than that given in the original description. A further difference, which applies to the asexual as well as the sexual forms, is in the color of the pigment, which is yellowish-brown, particularly when the granules are small. 3. The mean number of merozoites per schizont was found to be 6.09 ± 0.29, with a range of from three to ten. 4. The proportion of schizonts is usually low in this species, even when segmentation is most active, and frequently does not exceed 10 per cent. This is especially true in the later stages of the infection, which suggests that the mortality of the developing parasites is always high, and especially so after the host has had time to set up an effective resistance. 5. The proportion of young parasites in the younger erythrocytes was determined in one bird, from a series of smears made at different times during the twenty-four hours, and found to be high, but nevertheless considerably lower than that found in the other species of avian plasmodia so far critically examined—cathemerium, praecox (relictum), elongatum and circumflexum. 6. Exoerythrocytic stages were searched for in six birds, but without success.

Note on the Etiology of Verruga as Deduced from a Study of the Asexual Stages of Bartonella

Dec. 4, 1915, the writer presented before the Biological Society of Washington a paper on the identification of the asexual stages of Bacrtonella bacilliformis, the causative organism of verruga, which was published in the Dec. 19, 1915, issue of the Journal of the Washington Academy of Sciences. Jan. 7, 1916, he presented the same subject before Section VIII of the Second Pan-American Scientific Congress, during which presentation he announced certain points additional to those previously announced. This second paper will be published in due course in the Proceedings of the Congress, but it is desirable to place on record at once the additional points announced therein. They are as follows, and should be added to the paper published Dec. 19, 1915: The toxin resulting from the extensive asexual multiplication of Bartonella in the vascular endothelial cells of the subcutaneous tissues is liberated in quantity into the blood, causing the rise of temperature which marks the fever stage of verruga, the anemia following through hemolysis. The proliferation of vascular endothelial cells incited by this toxin not only imprisons the toxin itself, thus arresting the hemolysis, but also prevents the erythrocytes from coming into direct contact with endothelial cells containing merozoites of Bartonella, thus cutting short the infection of the erythrocytes. As the natural result, the fever and anemia both subside, and the gametes of Bartonella are no longer to be found in the peripheral blood. The infected endothelial cell, in situ in the capillary wall, is positively chemotropic for uninfected freshly oxygenated erythrocytes, attracting and holding them in contact with itself until transfer of a certain number of merozoites of Bartonella has been effected, the presence of which reduces the oxygen tension in the substance of the erythrocytes, thereby transforming their tropic qualities, the sufficiently infected erythrocytes being set free through negative chemotropism. The localized proliferation of vascular cells following verruga eruption-tissue inoculations is not due to any new activity of a living organism or virus. The reason why Drs. Strong ct al. were unable to obtain proliferation lesions by injection of a filtrate from these tis-