The American Journal of Tropical Medicine and Hygiene - Volume 5, Issue 1, January 1956

Observations are reported on a group of nearly 100 patients with sporozoite-inoculated Plasmodium vivax (Chesson strain) treated with chloroquine. Included was the treatment of 83 primary attacks and 101 relapses. Two treatment regimens were used: 1.5 grams base orally or 0.4 gram base intramuscularly. The primary attacks responded rapidly to treatment with either regimen. All cases followed sufficiently long were found to relapse after treatment. Of these, 45 were treated with 1.5 grams and 8 with 0.4 gram; there was no appreciable difference between the two where the treatment-to-relapse interval was concerned. The severity or duration of the primary attack prior to treatment could not be related to the treatment-to-relapse interval, nor could the number of infective bites used to induce the infection.

Relapses were treated as they occurred with one of the two regimens and were followed to further relapse or to conclusion in a number of cases. Treatment-to-relapse intervals were about the same after each attack; there was no difference in intervals after 1.5 or 0.4 grams dosages of drug. Twenty-five of 30 first relapses showed renewed activity after treatment, as did 17 of 19 second relapses, 7 of 10 third relapses, and two of four fourth relapses. One of the fifth relapses showed renewed activity.

Immunes inoculated with sporozoites usually experienced a short clinical course and, after treatment, a single asymptomatic parasite relapse.

Relapses occurred later and less frequently after treatment of extended clinical attacks than was the case in those attacks terminated prior to extensive clinical malaria, as reported by others in experimental work in volunteers.

It is concluded that in the Chesson strain of P. vivax extreme variability in patterns of infection and relapse is the rule in cases of the type considered.

A strain of Plasmodium gallinaceum was made 800-fold resistant to pyrimethamine. The strain was found to be resistant to several other 2,4-diaminopyrimidines, chlorguanide, and a diaminotriazine at the highest dose tolerated by the chicks. These data are compared with those obtained earlier when the strain was only 64-fold resistant to pyrimethamine and these differences are discussed.

The following kinds of mice were infected intravenously with Plasmodium berghei: white Swiss, C 57 Leaden × A, STR × C 57 Black, (C 57 Black × DBA) × DBA. They were examined daily for total per cent parasitemia; per cent mature erythrocytes infected, per cent immature erythrocytes infected, per cent erythrocytes which were immature, and total red cell count.

There was a peak infection of mature erythrocytes at the beginning of the second week, after which infection in these cells declined to a very low level. The infection in immature erythrocytes rose rapidly in all mice and reached a plateau of about 90 per cent in 4 to 6 days. The proportion of immature erythrocytes to total erythrocytes rose after the first week to a plateau of about 60 per cent. Total parasitemia reflected the initial peak of mature erythrocytes followed by the rise in the proportion of immature erythrocytes, most of which were infected.

The red blood cell count began to drop by the third or fourth day after inoculation. It fell more rapidly in Swiss mice than in the others, but there was little difference among the other mice in this respect.

A more detailed examination was made of the course of the infection in mature erythrocytes. The Swiss mice had a mean count on day seven of 51 per cent; (C 57 Black × DBA) × DBA, 21 per cent; C 57 Leaden × A, 11 per cent; STR × C 57 Black, 6 per cent.

In general, the higher the infection in mature erythrocytes, the shorter lived the mice. There were exceptions and these were discussed. Also discussed was the coincidence of peak infection of mature erythrocytes and the first mode of a bimodal survival curve.

Certain of the findings of a survey of the prevalence of intestinal parasitic infections in Forsyth County, North Carolina, have been previously reported (Mackie, T. T. et al., 1955). These relate to the prevalence of Entamoeba histolytica, the mass treatment of amebiasis and certain aspects of the epidemiology of the infection. The survey was directed primarily to the examination of 1,934 school children, white and Negro, urban and rural, constituting a representative sample of the schoolchild population of Forsyth County, the examination of family members of children found to be infected by E. histolytica and to the examination of a comparable group of negative control families of apparently uninfected children.

A prevalence of 6.1 per cent infection was found among the school children examined. Similar investigation of a total of 94 families of children infected by E. histolytica revealed a prevalence of 34.1 per cent, or an average of 2.2 cases of amebiasis per family.

Previous reports have presented different aspects of the findings of a survey of intestinal parasitic infections conducted in Forsyth County, North Carolina. These investigations were undertaken because of the paucity of general information relating to the area under consideration and because of discrepancies between the observed prevalence of Entamoeba histolytica among patients at the North Carolina Baptist Hospital in Winston-Salem and the prevalence of amebiasis as indicated by the morbidity data of the State Department of Health. Since it was necessary to offer treatment to infected persons in order to obtain maximum cooperation in the survey, ambulatory treatment by diiodohydroxyquin (Diodoquin) was made available to all individuals found infected by E. histolytica. The primary group examined, children in elementary schools, was utilized for a detailed study of familial amebic infections and to evaluate the usefulness of the examination of school children as a case-finding technique.The examination of urban family members revealed an unexplained higher prevalence of E. histolytica among the Negro than among the white families.

The effect of strain-specific rabbit anti-serum on the ability of cultures of E. histolytica to ingest rabbit RBC has been studied. These sera have shown marked ability to inhibit the phagocytic activity of the homologous strain of E. histolytica and varying ability to inhibit the phagocytic activity of heterologous strains. One strain, K-9, appears to be quite different from six other strains when tested in this way. The other six strains have exhibited varying ranges of heterogeneity. It is suggested that these results indicate antigenic variation among strains of E. histolytica. Other experiments are necessary to provide final proof.

Entamoeba histolytica was cultivated with a mixed bacterial flora through 15 transfers in 30 days in a medium containing inorganic salts, rice powder, glucosamine hydrochloride, and gelatin. The glucosamine could not be replaced by glucose, nor by any of a series of organic amines and amino alcohols. Gelatin could be replaced by serum proteins and the enzymatic digests of certain proteins. It could not be replaced by casein, edestin, lactalbumin, blood fibrin, nor by glycine or a mixture of amino acids based on the composition of gelatin.

Fumagillin, a new antibiotic, was tried in daily doses varying from 60–200 mg. in the treatment of acute amebic dysentery. The course was given usually for a period of 8–10 days. In the maximum daily dose of 200 mg., the drug was found effective in the symptomatic cure of the disease, while the Entamoeba usually disappeared from the stools 3–6 days after the start of treatment. Doses smaller than 100–150 mg. daily were inefficient.

Fumagillin was found however less effective than oxytetracycline or chlortetracycline, while the relapse rate after treatment was higher. Fumidil®, another drug of the same structure as fumagillin, was found more effective than fumagillin even when given in smaller doses. A dose of 60 mg. daily for a 10 day course was almost equal to 200 mg. daily dose of fumagillin given for a similar period. It is probable that Fumidil as used in this work was found more potent than fumagillin because the latter lost its potency by storage before use. Refrigeration is required to retain potency.

Side effects after both drugs are uncommon but include skin rashes and dermatitis, possibly of allergic origin.

Neomycin, another antibiotic, was found ineffective in the treatment of acute amebiasis when used in a daily dose of 4 grams for a period of 6 days. Its addition to fumagillin proved slightly better than either drug used alone.

The trial of a combination of fumagillin with oxytetracycline was found more promising and will be continued.

Erythromycin was found of value in the treatment of acute amebic dysentery. The drug was given to ten cases in a dose of 1.2 gm. daily for a period of 10 days and in a similar dose to another group for a period of 5 days. Marked improvement appeared in both groups, but two cases relapsed in the second group, while no relapses occurred in the first. The follow up is not complete however, as it was continued only for an average of 3 months. It is suggested that further trials be made, with a longer period of observation.

• 1.  Mosquitoes, ticks, houseflies, and probably human body lice were found to be susceptible to parenteral infection with West Nile virus. Chicken mites, bedbugs, rat fleas, hippoboscid flies, and cockroaches proved to be refractory.
• 2.  Culex univittatus, C. antennatus, and C. pipiens were infected readily when blood having a virus titer of 4.5 was ingested. A titer of 2.5 was sufficient to infect many individuals.
• 3.  C. pipiens and C. univittatus became infected and were capable of transmitting the virus when kept at mean daily temperatures of 12–23°C.
• 4.  C. univittatus transmitted the virus as soon as 5 days after the infective blood meal and for at least 33 days thereafter at 28–32°C.
• 5.  The tick Ornithodoros savignyi, when infected parenterally, transmitted the virus while biting infant mice, and the virus was isolated from the coxal fluid. This tick was also infected by feeding on the blood of infected mice, but failed to transmit the virus when infected in this manner. Ornithodoros erraticus and Argas persicus showed evidence of infection but did not transmit the virus.

This investigation confirmed and extended the work of Hammon and Reeves (1943) which demonstrated that the mosquito Culex tarsalis is capable of transmitting Western equine encephalitis virus from bird to bird. Virus was transmitted from chicken to chicken, from canary to canary, and from canary to chicken; 131 transmissions of virus were obtained in the study, and 29 (22 per cent) of the agents transmitted were re-identified by neutralization test.

Infectivity was acquired by these mosquitoes only when they fed on a bird with a threshold, or greater, level of viremia. This threshold level, of viremia was shown to be not more than an LD50 titer of 3.2. The minimal extrinsic incubation period was found to be four days, and it was further demonstrated that the rate of transmission steadily increased from 10 per cent on the fourth day to 84 per cent after the thirteenth day following the infective blood-meal. Transmission was readily accomplished by the bite of a single infective mosquito, and virus was transmitted by such a mosquito as often as four times in eleven days. Virus transmission was obtained from mosquitoes as late as sixty days after they had had an infective blood-meal, and from these results it is presumed that mosquitoes can remain infective for life.

Negative results were obtained in all attempts to demonstrate transovarian passage of western equine encephalitis virus in C. tarsalis. One mechanical transmission of virus by C. tarsalis was obtained in 24 attempts, suggesting that this phenomenon may also occur in nature, but the epidemiologic significance is not known.

A report is presented of the results obtained in a study designed to test the hypothesis that avian malaria plasmodia acquire and retain, for considerable lengths of time, the virus of Western equine encephalitis in infected birds. Experiments were performed to determine the virus concentration of plasmodia-infected blood cells from canaries concurrently infected with both agents and in blood cells from canaries infected with the virus only. The duration of viremia in birds suffering concurrent infection with both agents and in canaries infected with virus only was also determined. These and other studies failed to support the stated hypothesis. Quite the contrary, it was found that concurrent infection of canaries with avain malaria and with encephalitis virus resulted in a significant suppression of virus titer in such birds. This virus titer suppression could not be correlated with the degree of parasitemia, and did not occur in birds in the latent stage of malaria infection.

Concurrent infection of the mosquito Culex tarsalis with the avian malaria parasite Plasmodium relictum and Western equine encephalitis virus did not detectably alter the ability of this mosquito to transmit virus. Mosquitoes with such concurrent infections transmitted virus in 42 per cent of all attempts, whereas mosquitoes infected solely with virus transmitted in 45 per cent of all attempts. It was pointed out, however, that results of viremia studies on canaries, indicate that concurrent infection of such birds with the two agents suppresses the level of viremia, and that some birds develop virus titers too low to render mosquitoes infective. The possible importance of this phenomenon in the epidemiology and epizootiology of Western equine encephalitis is discussed.

To obtain information on the prevalence of histoplasmin sensitivity in Indonesia and its relation to radiographic evidence of pulmonary calcifications, a preliminary survey including simultaneous skin-testing with histoplasmin and tuberculin and X-ray examination of the chest was carried out in Djakarta Java in 1953–54. The study population comprised a total of 2,542 persons—795 university students, 267 patients in a general hospital, 458 nurses and 1022 schoolchildren.

The survey results indicate that skin sensitivity to histoplasmin is at least moderately prevalent in Indonesia; 2.7 per cent in the school-age group and from 9 to 12 per cent in the adult groups had sizable reactions to histoplasmin (6 mm. or more of induration). In all four groups the percentage was somewhat higher for the males than for the females. Among the nurses and the students those coming from West Sumatra had the highest percentage of positive histoplasmin reactions and those coming from North Java the lowest; the difference, however, was not very marked. The simultaneous tuberculin test was negative in about one-third of the histoplasmin reactors.

Out of a total of 2,311 persons X-rayed, only 25 or 1.1 per cent had pulmonary calcifications. For the adult groups the corresponding percentage was 1.5. Almost all of the calcifications were found in persons positive to tuberculin, yet the proportion of calcifications was higher among those positive to both tuberculin and histoplasmin than among those positive to tuberculin only. This suggests that histoplasmosis as well as tuberculosis is a cause of pulmonary calcification in Indonesia.

Egyptian village children in the first six months of life, while exposed to a highly endemic environment and experiencing a higher incidence of diarrheal disease, were less frequently infected with Shigella organisms than were older children. Shigella organisms were not recovered from infants in the neonatal period even during seasons of high incidence of infection in older subjects. Shigella infections were most prevalent during the second and third years of life.

A method for rapid isolation of S. typhi from blood clot is presented. The medium used consists of a Wilson & Blair agar slope in a four-ounce bottle to which is added 15 ml. of streptokinase bile salt broth. Positive results may be obtained in less than 24 hours.

Sending stool specimens to a distant laboratory for bacteriologic identification has always been unsatisfactory. The dried filter paper technique has proved to be an efficient, simple and cheap solution of the problem.

TECHNIQUE

On a clean piece of filter paper 6 to 10 drops of stool are placed and dried at room temperature. For dysenteric stools the mucous parts are selected. A firm stool should be mixed with water to make it semiliquid before dropping it on the filter paper. To obtain satisfactory results the following procedure should be performed:

• 1.  The stool should be dried as soon as possible after defecation.
• 2.  It is essential to dry thick fecal drops; thin drops are unsatisfactory. To reduce the drying period to not more than three hours thick drops should be made having a diameter of about 0.5 cm. consisting of about 0.2 cc. of mucus or stool. The drops should be separated about 5 cm. from each other to allow the moisture to be absorbed by the surrounding paper.

Thirty-six macaques (29 from Formosa, 3 from Japan and 4 from the Philippines) were exposed to S. japonicum cercariae of three geographical strains (Formosan, Japanese and Philippine). The degree of susceptibility of the monkey species to the strains of the parasite was ascertained by the length of the prepatent period, the number of eggs produced, the immature-mature egg ratio, and the number of adult worms at autopsy.

The results of the experiments showed that the Formosan monkey was highly susceptible to the Japanese and Philippine strains but was a relatively poor host for the Formosan strain. On the other hand, the Philippine and Japanese monkeys made reasonably good hosts for the Formosan strain of the parasite. This indicates that the Formosan strain of S. japonicum differs from the Japanese and Philippine strains.

In Schistosoma mansoni infections in Saudi Arabia a cure was obtained in 6 out of 12 cases with lucanthone hydrochloride (Nilodin) in dosages of 55 to 75 mg./kg. body weight, and in 12 out of 18 cases with sodium antimonyl gluconate (Triostam) in dosages of 13 to 21.6 mg./kg. body weight. In S. haematobium infections, one case was cured with 110 mg./kg. of lucanthone hydrochloride and 4 out of 4 cases were cured with 20 to 24 mg./kg. of sodium antimonyl gluconate.

A fatal case of bleeding gastric varices, resulting from cirrhosis of the liver produced by eggs of Schistosoma mansoni and associated with worms in the varices, has been presented. Factors that might account for the unusual location of the worms and the possible significance have been discussed. It is suggested that a careful post-mortem search of the cardio-esophageal veins in similar cases of persons who had lived in endemic foci of schistosomiasis might lead to the discovery of worms in this ectopic position.

Of 152 cases of Acanthocheilonema perstans infections in a Uganda labor force, 39 were hospitalized because of symptoms which in 7 cases were unusually severe.

Treatment with diethylcarbamazine by mouth even in large doses failed to achieve a permanent cure, and injection of the drug into the abdominal cavity was tried in 2 cases. The first relapsed but the other, which received a combined oral and intraperitoneal course of treatment was probably cured, since the blood remained negative for microfilaria for seven months, when examination was discontinued.

Anopheles quadrimaculatus mosquitoes which had been exposed to infection with Plasmodium vivax or P. falciparum were topically treated with a sub-lethal dose of DDT in acetone. No lethal effect due to the insecticide was evident on the developing parasites. However, surviving mosquitoes were so adversely affected by the DDT that there seemed little chance they would successfully transmit the disease.

At a temperature of 26°C. oocysts of P. berghei in A. quadrimaculatus fed on infected white mice contained sporozoites by the 6th day, with a peak number of oocysts containing sporozoites on the 9th day. The decrease in proportion of sporozoite-bearing oocysts after this time indicated that migration of the sporozoites to the salivary glands would normally take place at this time. However, infected glands were never found. Development of P. berghei to the oocyst stage was also obtained in two additional species of Anopheles not previously reported. Two species of culicine mosquitoes showed no evidence of infection with P. berghei.

Attempts to obtain sporozoite-induced infections in mice, rats, and hamsters by intravenous and intraperitoneal inoculation of stomachs with large numbers of mature oocysts, salivary glands or entire mosquitoes were unsuccessful.

The rodent host used as a source of the infecting blood meal appeared to be an important factor in the percentage of mosquitoes infected and oocyst development. A higher percentage of A. quadrimaculatus became infected and the number of oocysts per infected mosquito stomach was greater when mice were used as the source of the infecting meal than was the case when the same species of mosquito was fed on rats or hamsters. In addition, sporozoites developed more readily in mosquitoes whose infective blood source was mice.

The time of feeding with respect to the parasitemia peak in the rodent host had a most pronounced effect on the percentage of mosquitoes infected. Rodents in the early stages of the disease were more infective for mosquitoes than were rodents at or past the parasitemia peak.

The course of the Kasapa strain of P. berghei was determined for a small series of mice inoculated intravenously and hamsters inoculated intraperitoneally with a counted number of parasites. With 3 different sizes of inoculum the patency of the infection in white mice was delayed with the smallest dose, although the average day of death was about the same for the three groups. A ten-fold difference in inoculum seemed to exert little influence on the duration and course of the parasitemia in intraperitoneally inoculated hamsters.

In 1952 the Egyptian Ministry of Health regarded the Egyptian house fly, Musca domestica vicina, as developing such serious resistance to the chlorinated hydrocarbon insecticides that they recommended the discontinuance of such materials for general house fly control. A study was made to determine the resistance of house flies from localities where insecticides had been used for several years but where no treatment had been undertaken for at least one fly season. Flies from 11 localities in or near Cairo were tested with topical applications of acetone solutions of DDT, lindane, pyrethrins, and parathion. From the LD-50's computed from 24-hour mortalities, none of the strains tested showed a high degree of resistance.

Six weekly applications of BHC dust containing 1.3 per cent of gamma isomer to breeding places in one village where a similar treatment had previously been effective did not control the flies, and by the seventh week after the initial treatment resistance had increased at least threefold. These results indicate that with the cessation of treatments with chlorinated hydrocarbon insecticides Egyptian house flies lose resistance, but that resistance rapidly increases with reapplications of these materials. It is therefore recommended that other types of insecticide or techniques be employed to control this serious pest.

Uniforms impregnated with insect-repelling compounds M-1960, M-2065, and M-2066, after an initial washing, afforded complete protection against the terrestrial leeches Haemadipsa zeylanica and H. picta of North Borneo. After four more washings these compounds still gave protection, although the repellency was not complete. After six washings, the repellent effects of all compounds were not sufficient to be of practical value. No noteworthy differences in repellency of the compounds were noted. Impregnated socks were found to be an effective and feasible method for protecting scantily clad indigenous people against attacks of leeches that attach to the host below the knee.

Chemotherapy of Malaria, by G. Covell, G. R. Coatney, J. W. Field and J. Singh, 121 pp., French edition in preparation. Geneva: World Health Organization Monograph Series No. 27, 1955. 17/6. Sw. fr. 10-, $3.25 (cloth).

An Attempt to Control Leprosy by B. C. G. Vaccine in the Loyalty Islands, by Médecin-Capitaine des Troupes Coloniales Lacour, Directeur de l'Institut Pasteur de Nouméa, 45 pp. illustrated with maps and charts, paper cover, mimeographed. Sydney, Australia (Box 5254 G. P. O.): The South Pacific Commission, 1955.

Dried B. C. G. Vaccine, by Yoji Obayashi, M.D., WHO Monograph Series No. 28, 1955. Columbia University Press, International Documents Service, 2968 Broadway, New York 27, New York. $5.00, cloth.

Pharmacopoeia Internationalis (International Pharmacopoeia), first ed., vol. II. Recommended Specifications, by World Health Organization, xx + 350 pages, published also in French. Geneva: World Health Organization Pharmaceutical Section, 1955. 1/15, Sw. fr. 20-, $6.75.

La Lèpre, by Roland Chaussinand, second ed., 310 pp. illustrated with 18 in color. Paris: Expansion Scientifique Française, 3,800 fr.