The American Journal of Tropical Medicine and Hygiene - Volume 6, Issue 5, September 1957

A number of examples from recent research are given of the influence of protein and amino-acids on the metabolism of infecting organisms; of infecting organisms on host metabolism; and of the role of protein in determining the susceptibility and resistance to infection and its course when established. A comparatively neglected aspect of the subject of host-parasite relationships is the effect of the zymotic disease factor on the nutritional status of the host. Some success may attend treatment either by dietary means or by eradication of the infecting agent. There are however grounds for believing that for complete recovery a two-pronged attack is likely to be necessary. Also, even if the nutritional defect is predominantly of protein origin, it will no doubt be found that the best results will follow rehabilitation on a diet adequate and balanced in all respects. It is also noted that the repletion of protein-depleted subjects may require many months of protein feeding at levels above that to which the diseased patient had been accustomed.

Fat-balance studies were carried out in twelve cases of tropical sprue in Puerto Rico and in two volunteer control subjects. The investigation involved determining by chemical analysis the total daily fat in a screening diet given over an eight-day period and the total daily fat eliminated in the feces during the same period. Steatorrhea, defined as a daily output of over 6 gm. of fat (fatty acids) in 24-hour stools, was observed in ten of the twelve cases studied and in neither of the control subjects.

These data were gathered over a period of 5 years from the out-patient and medical services of the Arabian American Oil Company. The main factors determining the health conditions of the Eastern Province of Saudi Arabia are the subtropical desert climate, the concentration of the settled population in limited areas in oases or along the coast, and the way of living of the people. The climatic and environmental factors characterizing the area are probably responsible for the absence of major epidemics, but such communicable diseases as tuberculosis, eye infections and various protozoal and helminthic parasitoses are endemic at a high level. The oil industry has given a sudden impulse to the development of the area, resulting in urbanization and increased traffic, but also in the creation of medical and public health facilities, and in an attempt to solve local problems by basic sanitation and education.

A preliminary announcement that pyrimethamine (Daraprim®) sterilizes Plasmodium vivax (St. Elizabeth strain) gametocytes was made in 1953 by Coatney et al. The present report gives the details of these observations. The malaria had been induced in neurosyphilitic patients. Medication consisted of a single 25-milligram tablet of pyrimethamine given orally.

Anopheles quadrimaculatus, Q-1 strain, was used to test infectivity of the treated patients to mosquitoes. Control mosquito feedings were made on all patients from one to four hours before drugging. Infections in these mosquitoes demonstrated the presence of viable gametocytes.

Mosquitoes were fed at four-hour intervals for the first 24 hours after treatment on Patient number 1; otherwise all feedings were approximately at 24-hour intervals from time of dosage until at least no more gametocytes could be demonstrated in the smears.

Parasites and gametocytes were counted on Earl-Perez smears made at the time of feeding. Such smears were continued for 7 to 28 days after the disappearance of parasites.

The suppressive and prophylactic action of puromycin was tested on patients of a mental hospital who were exposed to a high rate of infection with intestinal protozoa. In an exposed group of cases receiving 100 mgm. of the drug daily for 10 days, about half the amebic infections were cured and most of the rest were suppressed. Weekly administration of as much as 500 mgm. for 5 weeks effected few cures and failed to prevent new infections.

A group of patients on a heavily infected ward were then cleared of protozoa with one gram of puromycin daily for 4 days, and about half of these were continued on a prophylactic regimen of 250 mgm. thrice weekly for 6 weeks. The unprotected group began to acquire infections during the 4th week after cessation of treatment, while the rest remained uninfected throughout the 6 weeks of prophylaxis, although constantly exposed. Two weeks after prophylaxis was discontinued, this group also began to acquire infections.

All the patients receiving one gram daily had diarrhea on the 4th day and a few vomited, but these reactions disappeared on reducing or withdrawing the drug. The lower dosages did not produce side reactions.

It was found in our laboratory that guinea pigs on a commercial diet did not develop an Entamoeba histolytica infection of a high order and the substitution of a synthetic diet was necessary to produce a severe, fulminating type of infection. The present study was conducted in an effort to obtain some evidence as to why it has been necessary to use the synthetic diet, and to secure information as to how the diet per se influenced the development of the experimental infection. The synthetic diet was shown to cause histologic alterations in the cecal mucosa of guinea pigs which were not evident when these animals were maintained on the commercial ration. These alterations consisted of a thinning of the mucosa and a dilatation of the glandular area with vacuoles indicating secretory retention. It is postulated that the diet may have conditioned the wall of the guinea pig's cecum to permit invasion by the symbiotic amebas and bacteria. The significance of these findings is difficult to assess, but they suggest that diet, quite apart from any deficiencies, may cause tissue disturbances in specific organs for which a given parasite has an affinity, and thus predispose them to infection.

A total of 140 Memphis, Tennessee cats were studied parasitologically by means of the subinoculation of brain tissue into uninfected white mice, and Toxoplasma gondii was recovered from 34 (24.3 per cent). Similarly, four out of 35 Columbia, South Carolina cats were shown to be infected. There was little difference in prevalence by sex, but smaller cats were less frequently infected than large, mature cats.

Serological studies by means of the dye test indicated even higher prevalences, as 64.2 per cent of the Memphis sample and 28.6 per cent of the Columbia sample had positive titers. In each of the subsamples, the ratio of the number of dye test positives to the number of demonstrated infections was 2.4 to 2.8. Of the cats with dye test titers of 1:256 or over, almost all were shown to be infected parasitologically as compared with half of the cats with a titer of 1:64. Lower titers were associated with lower percentages of recovery of parasites, and only in a single instance were parasites recovered from a serologically negative cat.

A Papuan native boy aged about 14 years died of acute encephalitis at Port Moresby in May 1956. A virus, isolated from the brain, has been identified as a strain of Murray Valley encephalitis virus and designated MVE-1-56.

Surveys of the rural population of Panamá for protective antibodies against yellow fever, conducted with serums collected in 1937 by Johnson (1938) and in 1941–1942 by Kumm and Crawford (1943) indicated that jungle yellow fever was endemic in San Blas on the Atlantic side of the Continental Divide and in Darien and the lower half of the Province of Panamá (adjacent to Darien) on the Pacific side. In recent years, however, extensive vaccination has limited the epidemiological value of such studies of the human population, and forest animals, especially monkeys, have been substituted. In the wake of the 1948 outbreak of jungle yellow fever in Panamá, Clark (1950) undertook a general survey of shot forest animals finding a high proportion of all bloods positive for neutralizing antibodies. The author simultaneously began a study of captured forest animals, housed, bled and tested at the Gorgas Memorial Laboratory.

An agent was isolated from Aotus monkeys, and was identified as belonging to the encephalomyocarditis group of viruses.

During the recent smallpox epidemic at Tabriz, 123 cases of smallpox and 17 deaths occurred. About 92 per cent of the population was vaccinated within three weeks, abruptly terminating the epidemic. Interesting features of the epidemic included: an instance of transmission by fomites; the occurrence of a second attack of smallpox in one individual; and a marked preponderance of female cases, attributed to less vaccination of females in this cultural area. The susceptibility to vaccinia of persons over 35 and the absence of smallpox in this group indicated that following vaccination immunity to smallpox may persist longer than immunity to vaccinia. Failures of vaccination in the past were attributed to the use of glycerolated vaccine without adequate refrigeration facilities. The use of lyophilized vaccine was proposed.

Three reports previously overlooked describe an encephalitis of horses that occurred in three coastal counties of Massachusetts in 1831. The disease appeared in midsummer, reached its peak in August and disappeared by the end of September. Mortality was high; of 100 horses known to be affected near Middleboro in Plymouth County, 75 died. Death usually occurred within one to four days after signs appeared. The affected horse first appeared dull and tended to move in a circle. Incoordination became marked as the disease progressed. Spastic paralysis, prostration and coma usually preceded death. Some animals that survived regained their health but others were killed because restoration to usefulness seemed unlikely. The only lesion seen on necropsy was a slight inflammation of meninges. The disease attacked animals of all ages. It was common among horses on pasture and rare in those kept stabled. The disease described in 1831 fits modern descriptions of Eastern equine encephalomyelitis.

• 1)  Complement-fixation tests with a soluble typhus antigen on sera collected from the indigenous population at various localities in Lower (Nile Delta) and Upper Egypt and the Southern Sudan revealed positive reactors in all three regions sampled. The highest percentage of positives was found in Lower Egypt (19.3), the next highest in Upper Egypt (13.2) and the lowest in the Southern Sudan (3.7).
• 2)  The rate of positives increases with the age of the donor.
• 3)  By utilizing specific epidemic and murine complement-fixing antigens, 35 of 50 current typhus infections were found to be of the epidemic type and 15 of the murine type.
• 4)  A high percentage (34%) of 116 rodents captured at Alexandria gave a positive complement fixation reaction, but none of 146 rodents captured in a village in the Nile Delta was positive.
• 5)  Though, since 1947, typhus has been at a low ebb—less than one case reported per 100,000 population—both louse-borne and murine typhus continue to occur, and in view of a growing-up, non-immune population and a developing resistance of the Egyptian lice to DDT, the danger, under favoring conditions, of epidemics in the future should not be ignored.

Serologic studies on cases of leptospirosis, that were observed in outbreaks among British security forces or sporadically among military and civilian personnel in Malaya from the end of 1953 through 1955, are reported. Paired or serial serum samples from 230 and single serum samples from seven proved or suspected cases of this disease were tested for the presence of agglutinins against 17 to 25 diverse serotype antigens. Significant titers were demonstrated in all but nine cases. In addition, leptospiral isolates from 93 of the above patients and 17 isolates from additional patients were identified through cross-agglutination and agglutinin-absorption tests. These studies disclosed the presence of jungle foci of infection with multiple leptospiral serotypes. The identity of the infecting strain by serotype or serogroup could be established either by cultural identification or serologic tests for 222 of 245 cases. In the remaining 23 cases, heterologous rises in titers, of the same order, against multiple serotypes precluded identification. A considerable proportion of patients showed agglutinins against heterologous “unrelated” serotypes. In many instances this may reflect simultaneous infections with multiple serotypes.

Specific limitations in the current scheme (Wolff and Broom, 1954) for classifying pathogenic leptospires pertinent to this study were noted, and modifications related to the recognition of “serotypes” and to the designation of serotypes were proposed.

The antigenic analysis of 110 leptospiral isolates disclosed the presence of 30 distinct serotypes. On the basis of modified criteria of the Wolff-Broom scheme 15 serotypes were identified as follows: Leptospira schuffneri (7 strains), L. canicola (2 strains), L. malaya (1 strain), L. mankarso (4 strains), L. pyrogenes (13 strains), L. australis B (2 strains), L. celledoni (6 strains), L. bangkinang (4 strains), L. autumnalis A (2 strains), L. pomona (1 strain), L. australis A (3 strains), L. grippotyphosa AB (9 strains), L. paidjan (11 strains), L. bataviae (1 strain) and L. wolffi A (7 strains). The antigenic characteristics of the remaining 15 serotypes have not hitherto been described and were designated and classified into the following serogroups: Canicola group—L. jonsis (7 strains), L. sumneri (1 strain); icterohemorrhagiae group—L. smithii (3 strains), L. birkini (1 strain); pyrogenes group—L. abramis (1 strain), L. biggis (8 strains), L. hamptoni (1 strain); javanica group—L. celledoni II (2 strains), L. coxus (2 strains); autumnalis group—L. mooris (2 strains); australis A group—L. fugis (1 strain); djasiman group—L. gurungi (1 strain); hebdomadis group—L. hemolyticus (4 strains), L. worsfoldi (2 strains), L. ricardi (1 strain).

Whipworm infections were completely eliminated in 87.5 per cent of patients who were treated orally with a dosage schedule of 200 mg. of dithiazanine three times a day for five days. The cure rate was 71 per cent when a dosage schedule of 200 mg. twice daily was employed. The anthelmintic spectrum of this drug also includes activity against Ascaris lumbricoides. The results of this study indicate that this compound is a very effective trichuricide which is suitable for oral administration.

A new anthelmintic compound, dithiazanine (3,3′diethylthiadicarbocyanine iodide), was found to be highly effective by oral administration against pinworms in mice, ascarids, hookworms, and whipworms in dogs, as well as ascarids and hookworms in cats.

Further investigations are necessary to determine if dithiazanine is effective in the treatment of such human helminthic diseases as ascariasis, oxyuriasis, trichuriasis and strongyloidiasis.

Immersion of motile specimens of Ascaris lumbricoides in piperazine solutions gradually results in paralysis of the worms. When the worms are split the muscle of the body wall contracts in response to acetylcholine. This response is rapidly blocked by dilute solutions of piperazine. Electrical stimulation of the muscle of the body wall also causes contraction. This contraction is not blocked by perfusion of this preparation with piperazine. This evidence indicates that piperazine produces paralysis of Ascaris by blocking the neuromuscular junction. This observation can account for the therapeutic effectiveness of piperazine against Ascaris. Ascaris muscle responds to several pharmacologically active compounds in a manner resembling vertebrate skeletal muscle.

Simultaneous fecal examinations were made of 400 samples by the following methods: direct, Faust, Bayona, Ferreira and Baermann; 103 samples were negative and in the remainder, 18 species of parasites were found. The direct method is indispensable for the finding of trophozoites. For cysts, eggs and larvae, the Ferreira method diagnosed a greater number of positive samples than the other methods. It was particularly effective when the number of eggs was small, providing richer concentrations. However, irregularity of excretion, particularly of cysts, makes more than one examination necessary.

Simulium damnosum, the main vector of human onchocerciasis over a large part of tropical Africa, shows no reluctance to attack and bite man in nature. In the laboratory, however, it has always proved to be an extremely refractory insect, most workers having experienced the greatest difficulty in persuading it to feed in captivity. This feature is not peculiar to Similium damnosum but is also exhibited by several other medically important species of Simulium, including the vectors of onchocerciasis in Central America.

As a result of this almost insuperable difficulty the great bulk of evidence incriminating Simulium as a vector of onchocerciasis has had to be based on the use of wild flies, the general method being to expose a suitable human subject to the bites of wild flies in the open and collecting the engorged flies in tubes.

A perfusion technique for selectively washing adult schistosomes from various portions of the portal system has been developed and tested on cadavers. Although the literature reports adult schistosomes from various areas of the portal system no method has previously been devised for determining the total worm burden in a given area. It is hoped that determining total worm burden in the host as well as burden in selected areas, by the methods here presented, will reveal more accurately the incidence of infection in a population and promote a better understanding of the relationships among clinical manifestations, total worm burdens, and areas of the body involved. It is anticipated that this preliminary report will be followed by application of the method in an endemic area of schistosomiasis and that further refinements of technique will follow.