The American Journal of Tropical Medicine and Hygiene - Volume 2, Issue 6, 1953

In Part I of this study six therapeutic regimens employing four different 8-aminoquinoline derivatives were tested under strictly controlled conditions in mosquito-transmitted Chesson strain vivax malaria, experimentally induced in volunteers in a Federal penal institution. Thirty-four men were treated with each regimen. Test drugs were given every 6 hours for 14 days, in combination with quinine sulfate, 250 mg. of base every 6 hours for the same period. The relapse incidence after primary attacks was as follows:

1. Primaquine 20 mg. (base) daily 15 per cent
2. Primaquine 10 mg. (base) daily 65 per cent
3. Isopentaquine 60 mg. (base) daily 35 per cent
4. SN-3883 60 mg. (base) daily 9 per cent
5. SN-3883 30 mg. (base) daily 21 per cent
6. Pamaquine 60 mg. (base) daily 82 per cent

Although toxic manifestations were not alarming with any of the compounds, primaquine at the effective dosage of 20 mg. per day was exceptionally well tolerated, and under the conditions of the test was regarded as the best of the four drugs.

Part II of the study dealt with the trial of three therapeutic regimens employing two different 8-aminoquinolines under the same conditions as outlined above. Ten men were treated with each regimen. The test drugs were given in a single dose daily for 7 days; chloroquine, 1.5 gm. (base) total dose, was given concomitantly during the first 3 days for the management of the acute attack. Relapse incidence after the acute attack was as follows:

1. Primaquine 30 mg. (base) single dose daily 90 per cent
2. Primaquine 20 mg. (base) single dose daily 80 per cent
3. SN-3883 60 mg. (base) single dose daily 100 per cent

There were no toxic manifestations, but the high relapse incidence indicates the limited curative efficacy of these shorter regimens against severe Chesson strain vivax infections and consequently that they are not generally applicable curative regimens.

Korean vivax malaria exhibits a bimodal pattern of clinical activity and a period of long-term latency similar to other strains of Plasmodium vivax originating in temperate climates. It was possible to define many aspects of the natural history of this strain with a fair degree of accuracy in large numbers of men infected in the field. The pattern of clinical activity of Korean vivax malaria is similar in all major respects to the pattern of the St. Elizabeth strain (Table 3). In the absence of reinfection during a second transmission season, Korean vivax malaria acquired in the field terminates spontaneously within two years. Negroes appear to be less susceptible to infection with this strain of vivax malaria than Caucasians. A follow-up period of four months is adequate to determine the effect of a therapeutic agent on the relapse rate, when the majority of attacks are late attacks.

Fifteen milligrams of primaquine base administered daily for 14 days, in conjunction with standard chloroquine therapy (1.5 gm. base or 2.5 gm. chloroquine diphosphate in 3 days), constitutes the treatment of choice for the radical cure of Plasmodium vivax of Korean origin during late clinical activity. This therapeutic schedule may be safely continued on an ambulatory basis with only minimum medical supervision after acute symptoms have subsided.

Clinically significant toxicity was not observed with either primaquine or pamaquine, although in the dosage employed pamaquine is potentially toxic in a small percentage of Negroes.

A study of the therapeutic effectiveness and toxicity of primaquine in daily doses of 10, 15, 20, and 30 mg. (base) daily for 7 or 14 days, administered concurrently with 1.5 gm. (base) of chloroquine in 3 days, at the time of an acute attack of vivax malaria of Korean origin is reported. The relapse rate in patients treated with chloroquine alone was 43.8 per cent. The relapse rate was reduced to less than 3 per cent by all regimens of primaquine used. These results indicate that a daily dose of 10 mg. of primaquine administered for 14 consecutive days is adequate for the curative treatment of vivax malaria of Korean origin. A daily dose of 20 mg. administered for 7 days was effective in reducing the relapse rate.

No significant toxicity was observed with doses of 10 and 15 mg. daily. A daily dose of 20 mg. of primaquine produced acute severe intravascular hemolysis in one of 14 Negroes. This dose was well tolerated by all other patients. Mild abdominal pain and cyanosis due to methemoglobinemia occurred in approximately one-fourth of the white patients treated with 30 mg. of primaquine daily, but these effects were not severe enough to interfere with normal activity.

In a study of the curative effect of 15 mg. of primaquine daily for 7 days against late attacks, the relapse rate in patients with Korean vivax malaria was reduced from 50 per cent in patients treated with chloroquine to 3 per cent in patients treated with chloroquine and primaquine. The minimum follow-up in any patient was 3 months.

In a study of the curative activity of primaquine administered during long-term latency of Korean vivax malaria, 294 soldiers, exposed to infection in the summer of 1951 were treated early in April, 1952 with 15 mg. of primaquine daily for 14 days. A control group of 331 men was given a placebo. None of the men treated with primaquine developed malaria during the next six months; 17.5 per cent of those given the placebo did develop malaria during the same period.

Since 1948, primaquine, a close relative of pamaquine, the historically important curative antimalarial agent, has been the subject of intensive clinical study at Stateville Penitentiary (Edgcomb et al., 1950; Hockwald et al., 1952; Clayman et al., 1952). More recently primaquine has been used on a large scale among military personnel (Alving et al., 1952). These studies have shown that primaquine is safe and practical for mass prophylaxis and therapy of malaria in nonimmune Caucasians and Negroes in a nonendemic area, and as such is the drug of choice for curative treatment of relapsing malaria (Alving et al., 1953).

There remain, however, two very important problems: (1) testing the tolerance of tropical native peoples to primaquine and (2) measuring the response of field infections to treatment with that drug. These problems involve several factors not present in previous studies. Very few tropical populations are well nourished.

Reported therapeutic tests show that pyrimethamine is an effective suppressant for malaria in dosage of 25 mg. single dose weekly. Our studies reported here and previously (Coatney et al., 1953) indicate that this dosage may be given safely to white or colored races without untoward reactions, barring possible cases of idiosyncrasy.

Determinations on the numbers of amebae obtainable from cultures of E. histolytica with 17 individual species of bacterial symbionts in whole-egg medium showed differences ranging from 20,000 to 450,000 amebae per culture.

E. histolytica-organism t could not be propagated through indefinite serial transfer in egg white medium even with enrichments of cholesterol and B vitamins. With enrichment of cholesterol the ameba was propagated in egg white medium with Escherichia coli and Aerobacter aerogenes, respectively, through indefinite serial transfer.

Evidence was obtained indicating that E. histolytica produces a gelatinase and/or a protease that liberates starch grains from particles of ground rice, and that rice proteolysis may be adaptive.

Using the Eldredge-tube method of measuring carbon dioxide, more of the gas was demonstrable from cultures of E. histolytica with two bacterial symbionts than from the symbiont alone except when glucose-enriched medium was used. The increase was attributable to substrate furnished through the metabolism of the amebae. No differences in production of carbon dioxide were demonstrable from cultures of E. histolytica-Clostridium perfringens, and of C. perfringens without amebae. This result was attributed to utilization of rice flour by C. perfringens.

Metacyclic Trypanosoma cruzi transforms in muscle tissue to a regressive trypanosome which broadens and thickens while changing from a ribbonlike to a crescentic body form, developing many volutin granules and vacuoles. The elongated, oval, laterally compressed nucleus becomes oval and then round while the oval kinetoplast becomes triangular. Disappearance of the trypanosome shape results in a rounded, regressive, transition parasite which, by shortening or disappearance of the flagellum accompanied by development of the rod shaped kinetoplast, becomes the regressive leishmaniform parasite.

Large size of all organelles characterizes the dividing leishmaniform stage. The reduction of volutin, vacuoles and cell volume, with retention of rod-shaped kinetoplast and round nucleus characterizes the progressive leishmaniform parasite. The progressive transition shows an oval kinetoplast and enveloping flagellum with undulating membrane forming. If elongation occurs, the parasite, by flow of the cytoplasm and nucleus along the line of growth of undulating membrane and flagellum, transforms into the short, stout trypanoform organism. If flagellar growth continues over the circular, progressive, transition cytosome, a V-shaped indentation appears between the base of the free flagellum and kinetoplast area and the parasite untwists becoming a stout, progressive trypanoform parasite.

These progressive trypanoform parasites, by subsequent slimming of the body, elongation and compression of the nucleus, and condensation of the kinetoplast, become the progressive trypanosome which on arrival in the peripheral blood becomes the broad, deeply basophilic regressive trypanosome with anteriorly displaced nucleus. Since leishmaniform stages differ in size, small forms develop into small, progressive, transition and eventually short, slender, progressive trypanosomes. Large, leishmaniform parasites elongate under tissue pressure, resulting in long, slender, progressive trypanosomes. Small, intermediate and large trypanosomes, under the changing chemical environment of the hosts' blood, transform into regressive trypanosomes which may reinvade the tissues and repeat the cycle.

In recent investigations Eyles and Coleman (1952) demonstrated that 2,4-diamino-5-p-chlorophenyl-6-ethylpyrimidine (Daraprim) prevented death of white mice experimentally infected with a strain of Toxoplasma gondii isolated from the Norway rat. Additional studies by Eyles (1953) showed that the antitoxoplasmal action of Daraprim was enhanced by sulfadiazine.

In experimental toxoplasmosis it is well known that chemotherapy with such agents as sulfonamides, sulfones and certain antibiotics may prevent death of mice during the period of drug administration. It has been repeatedly observed however that Toxoplasma may not be eradicated from the tissues of mice and that relapse and death may occur within a variable time following cessation of therapy. It has been observed here that treated mice may survive for several months or possibly for the duration of their normal life span yet retaining foci of virulent Toxoplasma in their tissues. It is questionable therefore whether survival of Toxoplasma-infected mice during the period of experimental chemotherapy constitutes a valid criterion of drug efficacy.

In vitro culture studies indicate that Thiolutin and its Propionamido-deacetyl derivative inhibit Trichomonas vaginalis in a concentration of 0.2 µg./ml. Netropsin inhibits in 12½ µg./ml., and streptothricin, Rimocidin and fumagillin in a concentration of 25 µg./ml. Terramycin, Neomycin, polymyxin, carbomycin (Magnamycin), polymyxin-terramycin mixture inhibit in a concentration of 125 to 250 µg./ml., while bacitracin and Viomycin are relatively ineffective.

Annual microfilarial counts have been determined for periods of 1, 2 and 3 years following the use of diethylcarbamazine (Hetrazan, Notezine) as a microfilaricide in a filariasis control program. Two dosage schedules have been employed: (1) Two mg. per kg. of body weight 3 times a day for 7 days, repeated at the end of the year on the individuals who remained positive, (2) 2 mg. per kg. of body weight 3 times a day, 1 day each month for a period ranging from 12 to 18 months. The results are recorded in terms of (a) percentage of the population positive for microfilariae, (b) average number of microfilariae per 20 cmm. of blood, and (c) the frequency distribution in the population of microfilarial counts per 20 cmm. of blood at six different levels. The results may be summarized as follows:

• 1.  Of 145 positive individuals treated with schedule (1) the percentage of positives was reduced to 17.5 at the end of the second year; the average microfilarial count per 20 cmm. dropped from 79 to 0.8; and the frequency distribution results showed marked reductions at all levels, no positives occurring above the 11–30 group.
• 2.  Field studies in areas where considerable migration of population occurs and where supervision of drug administration was not as rigid as in the above group, likewise exhibited marked reductions at the end of 2 years, but to a lesser extent.
• 3.  The second dosage schedule of 2 mg. per kg. of body weight 3 times a day, 1 day a month, for 1 year gives promise of being a practical method of administrating diethylcarbamazine in a filariasis control program.
• 4.  A possible “infection factor” based on the experimental results of Rosen in which mosquitoes were fed on man harboring different levels of microfilariae is suggested and a potential “infection rate” is determined from certain experiments in this program showing the frequency distribution at these same levels in man before and after the use of diethylcarbamazine.
• 5.  All data observed following the administration of diethylcarbamazine as employed in this study show marked reduction in the microfilarial rates. Whether these reductions are sufficient to limit the transmission of W. bancrofti to a level where clinical cases will cease to occur can be determined only by observation over a period of years.

Generally similar growth curves of Dirofilaria immitis larvae were noted in the following experimental mosquito hosts: Culex pipiens, C. quinquefasciatus, and their F2 hybrids; Aedes aegypti and A. albopictus; Anopheles quadrimaculatus and A. freeborni. The host constitution apparently had an effect upon the size attained by the filaria larvae, and the larval length/width ratio varied considerably between genera and also, in Culex and Aedes, between species, but to a lesser extent in Anopheles. Thus phylogenetic affinities between mosquito species do not necessarily imply similar growth of the dog filaria within them.

Third stage larvae undergo considerable change in length especially in favorable mosquito hosts. Nevertheless, at 20 days after the mosquito's infective meal the third stage filaria larvae still are to be found both as long and short individuals. Whether this is linked with sex differentiation is not known.

A total of 2,936 persons was examined in Central Thailand for the presence of Fasciolopsis buski. The results support the conclusion that this infection is endemic in the examined areas where water caltrops (Trapa bicornis) are cultivated. A correlation between the degree of water pollution and incidence of infection was observed in different districts. The highest incidence and intensity of infection was found among children 10 to 14 years of age. To the authors' knowledge this is the first time that fasciolopsiasis has been reported as endemic in Thailand.

A study of 65 cases of viper bite in Israel is presented; 61 cases from the north of the country were given full clinical investigation and 4 cases from the center of the country were investigated anatomo-pathologically only. The clinical appearances are summarized according to frequency and classified patho-physiologically. Four cases are described in detail. Anatomo-histologic investigations are described and accompanied by photographs. New observations are made on the pathogenesis of the signs and symptoms of the poisoning. Principles of first aid and medical treatment are laid down on the basis of 10 years of clinical experience and a critical study of traditional methods is made. New methods of treatment are suggested for clinical trial.

• 1.  The presence of A. albimanus in the island units of the Caribbean is discussed.
• 2.  Field observations have now established its absence from the Netherlands Leeward and Windward Islands, Trinidad and Tobago, Grenada, St. Vincent, Barbados, St. Lucia, Martinique, Dominica and St. Kitts. The southernmost point of its distribution in the island chain is established in Marie Galante at latitude 15°53′ N.
• 3.  In the Caribbean Islands A. albimanus is limited to Guadeloupe (and Marie Galante), Montserrat, Antigua, Nevis, Virgin Islands (St. Croix, St. Thomas and Tortola) and the Greater Antilles.

In the preceding paper Charles and Senevet raise a question concerning the accuracy of the identification of Anopheles albimanus which Seagar had reported from Barbados. Among the material in the collection of the Department of Parasitology, the Johns Hopkins University, there are four pinned adults (one male and three females) bearing the following label: “A. albimanus—Barbados—1928. Received Apr. 24.” There is also a slide mount of the terminalia of two males, and another slide on which is mounted some first, second, and two third stage larvae. These slides are labelled “Anopheles albimanus. Barbados, 1928” in the late Dr. F. M. Root's handwriting. Presumably all this material had been sent to Root for confirmation of identification, so that these specimens probably represent some of the original material taken on Barbados by Seagar.

Two of the females are in good condition and I would identify them without hesitation as being A. albimanus.

The total quantity of domestic refuse from a typical residential city block was measured for a period of 18 weeks during the summer of 1950. Samples of the refuse were selected at random for analysis and it was found that approximately 30 per cent of the refuse (by weight) was edible. Assuming that about ⅓ of this ration is always available to the rats, it is estimated that each rat was supplied with about 150 gm. of edible material per day.

For a more detailed analysis of the particular food items, 50 foods were selected on the basis of their ready availability to the rats in domestic garbage and were fed to groups of caged rats. The caloric content per 100 gm. of test food (cal) was obtained from the literature. In addition, three indices were calculated for each food from the results of 3-day feeding trials. The w index represented the percentage, at the end of a 3-day diet, of the rat's initial body weight. The c index represented the average daily consumption, per 100 gm. rat body weight, of a particular food, when no other food was available for a 3-day period. The p index represented the number of grams of test food eaten per hundred gm. of a standard food, both being offered simultaneously and to excess for 3 days. The standard food used was “Fox Checkers,” a complete-diet laboratory food manufactured by the Ralston Purina Company.

The problem of replication of measurements could not be dealt with as fully as might be desired. However, in order to get some indication of the magnitude of variation inherent in the indices, the standard diet was fed to 3 groups simultaneously. The results showed a considerable amount of variation in w and very little in c. Some of the variation in w is tentatively explained by group behavior phenomena.

From the relationship between w and cal, it is determined that the minimum energy requirement of rat food is about 137 calories per 100 gm. food.

The relationship between cal and c is somewhat suggestive of a hyperbolic function. If this hypothesis is valid, then it follows that a rat would strive for a definite amount of food value per day, rather than food volume.

Combining the two relationships described above, it is determined that rats require about 18.9 grams of moderately high caloric food per 100 gm. body weight per day. Therefore, the average (250 gm.) rat would need about 47 grams of food daily, and this figure agrees reasonably well with other estimates of rat intake. Despite the fact that about half (author's estimate) of the 150 gm. daily ration falls below the minimum energy requirement of 137 calories per 100 gm. of food, the quantity of food available was clearly in excess of rat needs. Therefore, it is suggested that food distribution, rather than quantity, may have governed the population of the block under study.

A close relationship was obtained between w and p. This is interpreted as meaning that rats prefer foods on which they will gain weight. It is suggested that some of the scatter in the points is due to avitaminosis, aversion to highly spiced foods, preference for sweetened foods, or a combination of these factors.

The relations were determined between the number of flies “visually estimated on a grill count basis” and then actually counted with a Scudder grill on 2,850 fly attractant sites. Eight two-man teams of inspectors collected these data throughout the 1951 “fly” season in Phoenix, Arizona.

The visual estimate technique agreed with the grill method by the same inspector with a range of 69 to 89 per cent accuracy. Agreement between inspectors was 89 to 98 per cent using actual counts, and 75 to 91 per cent using visual estimates. By application of simulated field threshold values to indicate the necessity for control action, the inspectors, with the exception of one team for visual method, were in agreement.

The results of this study show that the “visual estimate” technique is a useful extension of the Scudder grill method for appraising adult fly densities.