Avian Plasmodia Research Articles

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.

Prophylactic and Therapeutic Effect of Sulfonamide Compounds in Experimental Malaria

SummarySulfanilamide was found to have a prophylactic value and a marked therapeutic effect on acute P. knowlesi infections in rhesus monkeys. It had, in addition, a direct action upon the parasites in vitro.Sulfanilyl sulfanilate proved an ineffective prophylactic agent; it had no apparent in vitro action on the parasites, but some therapeutic value in acute P. knowlesi infection was noted.In chronic infections 3.0 g of sulfanilamide given intraperitoneally was sufficient to render blood non-infectious for susceptible monkeys, while the same amount of sulfanilyl sulfanilate was without effect.Sulfanilamide and sulfanilyl sulfanilate were ineffective for prophylaxis and had no therapeutic value when tested against infections produced by 2 different species of avian plasmodia.

The Occurrence of the Avian Malarias in Nature

Summary and ConclusionsIn the course of a survey which has so far covered a total of 652 birds, belonging to thirty-four different species, fifty-four cases of malaria have been found, a number of them mixed infections. The species of plasmodia represented have included the following, in the order of their frequency: Species Number of cases 1. Piasmodium praecox 23 2. Plasmodium cathemerium 12 3. Plasmodium circumfiezum 7 4. Plasmodium vaughani 6 5. Plasmodium elongatum 5 6. Plasmodium polare 4 7. Plasmodium ap.? 3 8. Plasmodium nucleophilum 1 This and other work indicate that at least the first five of these species are probably cosmopolitan in distribution (assuming that P. tenue and tumbayensis are the same as vaughani, as seems probable).Some of the species of birds found to harbor malaria plasmodia have apparently never been found so infected before. These include the following: 1. Catbird (Dumetella carolinensis) 2. Chipping sparrow (Spizella p. passerina) 3. Cliff swallow (Petrochelidon albifrons albifrons) 4. American crow (Corvus brachyrynchos brachyrhynchos) 5. Purple grackle (Quiscalus quiscula quiscula) 6. Slate colored junco (Junco hyemalis hyemalis) 7. Starling (Sturnus vulgaris vulgaris) 8. White throated sparrow (Zonotrichia albicollis) The results indicate that a considerable amount of host-parasite specificity exists even in bird malaria, at least with regard to certain species of parasites. This seems most marked in the case of P. vaughani which was found common in robins by Novy and MacNeal (1904) many years ago, and has also been found to be so by us. P. polare has also been found so far only in the cliff swallow.Subinoculation into English sparrows or canaries known to be free from malarial infection was used to supplement microscopic examination in 127 cases. The results showed it to be much superior as a means of diagnosis to anything else. In the case of the song sparrows it approximately trebled the number of positive cases, and it often revealed mixed infections when only one species of parasite had been originally found. It is also the only method by which subpatent infections can be satisfactorily diagnosed according to species.Since non-migratory birds and young birds show a very low incidence of infection with malaria, it is probable that most malarial infections are acquired in the southern portion of the range of migratory species. It is possible that in the case of P. vaughani the vector occurs only in the south, since young robins and the non-migratory types have never been found infected.The highest incidence of malarial infection was found in the robins and song sparrows, all the adult robins examined being infected, and about two-thirds of the song sparrows from which subinoculation was done. It seems likely that in some cases at least difference in frequency of infection with malaria can be accounted for on the basis of difference in habit or migratory range. Our results indicate that malaria is probably the commonest disease from which these species suffer, and our experience with malaria-infected canaries in the laboratory suggests that even though they survive the acute stage of the infection their lives may nevertheless be considerably shortened. Leucocytozoan and Haemoproteus infection is also common, but less frequent, but the latter has been found extremely common among chipping sparrows.It seems likely that as work of this sort is extended malarial infection will be found much commoner among wild birds than it has been thought to be in the past, and that the number of apparently distinct species of avian plasmodia will be increased. The possibility that some of these differences may be due to hybridization in the mosquito should be investigated.

Quinine and Plasmochin Therapy in Infections with Plasmodium Circumflexum

Summary and Conclusions The study here reported had for its object the investigation of the effects of quinine and plasmochin on infections with Plasmodium circumflexum, and comparison of the results with those already obtained by similar treatment of infections with the other four species of avian malaria (Plasmodium capistrani excepted). A total of fifty-five female canaries were used in the treated series. The results may be summarized as follows: 1. Basing the list which is given below partly on the data reported in the present paper and partly on data previously reported, the susceptibility of the five species of avian plasmodia here considered to treatment with quinine and plasmochin appears to be as follows, the most susceptible being given first: Quinine Plasmochin 1. Plasmodium rouxi 1. Plasmodium elongatum 2. Plasmodium praecox Plasmodium rouxi 3. Plasmodium cathemerium 2. Plasmodium praecox 4. Plasmodium circumfiexum 3. Plasmodium circumfiexum 5. Plasmodium elongatum 4. Plasmodium cathemerium It should be noted that in the first list (quinine) the differences between Praecox, cathemerium and circumflexum are very small, and that this is also true of praecox and circumflexum in the second list. Elongatum and rouxi are placed at the top of the second list, and rouxi heads the first list, chiefly because infections with this species could be readily sterilized with the drug in question. Cathemerium and circumflexum occupy the positions they do (even though plasmochin is effective in removing parasites from the peripheral blood in a relatively short time) largely for the contrary reason; in other cases the percentage of parasite-free days was the chief factor governing the place of the species in the scale. 2. As with the other species, Plasmodium circumflexum is more amenable to plasmochin than to quinine. When sterilization is not brought about relapse within a month generally occurs, but does so less frequently than in praecox infections, and may be deferred for two months or even longer. This is correlated with the fact that the parasite-level in chronic infections of circumflexum is generally established at a much lower level than in the case of praecox, and is to be compared in this respect only to cathemerium. 3. Plasmochin in combination with quinine is apparently no better than when used separately, and may even be less satisfactory—due possibly to quinine intoxication. 4. As with the other species, treatment during the incubation period is much more effective than when postponed until parasites appear. A considerable proportion of cases may be completely aborted in the former case, as demonstrated by continued freedom from relapse and by subinoculation, with subsequent reinfection, but so far no case in which parasites had already appeared has been sterilized. 5. There is little evidence that gametocytes are either more or less susceptible to plasmochin and quinine than the asexual stages. 6. Study of the rates of reproduction of the different species, and other peculiarities of the life-cycle, suggests that the degree of susceptibility to drug therapy may depend in large part on these factors—particularly in the case of plasmochin.

Quinine and Plasmochin Therapy in Plasmodium Rouxi Infections, with Further Notes on the Effects of These Drugs on the Other Avian Malarias 1

Summary and Conclusions The work herein described has had for its object the solution of the problem as to whether the two species of avian plasmodia most refractory to treatment could be more successfully treated with a combination of plasmochin and quinine, than with either drug used separately, and further investigation of the effect of plasmochin upon Plasmodium elongatum, shown in previous work to be very highly susceptible to plasmochin. Plasmodium rouxi, an Algerian species, has also been studied with reference to its chemotherapy and the results compared with those obtained by the same methods on the other three species. The question of the reliability of splenomegaly as an indication of malarial infection has also been investigated. A total of 120 cases have been treated, 44 have been used as controls, and 101 others have been used in testing for sterilization and in other ways. Allowing for duplications, 223 birds have been used. The following conclusions seem justified: 1. Infections with Plasmodium praecox and Plasmodium cathemerium can not be more successfully treated with a combination of plasmochin than with either drug separately, or at least such an advantage, if it exists, is slight. The results obtained in these researches gave no suggestion that such a superiority obtains. 2. Wide differences have been shown to exist in the susceptibility of different birds to treatment, when infected with Plasmodium elongatum, and these are interpreted as meaning that the effect of the drug used—plasmochin—is exerted indirectly, through a stimulation of some sort to the natural defensive powers of the host, as well as directly upon the parasite. In general, about four days of treatment appear to be necessary to prevent the development of the infection when started immediately after inoculation, and about twelve days appear to be required for sterilization when administration is deferred until parasites are evident in the blood. 3. Plasmochin exerts a direct plasmodicidal action, when parasites belonging to the species elongatum are exposed to the drug in vitro, but the action is slow and apparent only after a number of hours. Morphological changes are produced more quickly in the parasite than are changes in infectivity. 4. Plasmodium elongatum infections are less easily treated with plasmochin after they become chronic, but it is certain that the parasite level is forced down to a very low level—so low that the blood is no longer infective to clean birds—and that the level remains at this low point in most cases for at least two weeks, even though it is not fully demonstrated that sterilization occurred. 5. Infections with Plasmodium rouxi are as suceptible to plasmochin as are those of elongatum, and more susceptible to quinine than any of the other three species. Sterilized cases are as readily reinfected as when infected the first time. 6. The parasite-level establishes itself at a much higher point with chronic cases of Plasmodium rouxi than in chronic cases of any of the other three species studied. 7. Splenomegaly is not a trustworthy means of diagnosis in avian malaria, particularly chronic cases, since it may be absent, even when parasites are easily demonstrable in the blood, and is often present in birds dying from other causes and known to be, and to have always been, free from malaria. Even the color of the spleen is not a reliable indication, unless it is very dark.