The American Journal of Tropical Medicine and Hygiene - Volume 24, Issue 3, May 1975

During the long time that I have earned a living as an entomologist, I have been a member of several scientific societies; however, this is the one in which I have felt most at home. No other society offered the excitement and inspiration that I received at the annual meetings by listening to reports of studies on malaria, yellow fever, and other tropical diseases, especially those given by people engaged in field projects in what to me were exotic tropical countries. Furthermore, these were the workers whom I most admired, and to visit with them, however briefly, was another reason why those annual meetings I could attend were so meaningful.

All of us are fully aware of the difficulties facing some areas of biomedical research. In tropical medicine these are especially acute. The infectious diseases no longer are the killers they once were, and so the emphasis in medical research and training has shifted from them to the metabolic and degenerative diseases.

Amebas have been observed so seldom in the large intestine of man that even R. Leuckart, a thorough and experienced parasitologist doubted their existence and considered the only previously published case (by Lambl) to have been an example of abnormal cellular forms mistaken for amebas. The case at hand, which I had the opportunity to observe during the course of several months in Prof. Eichwald's clinic, therefore, is of great interest.

Case history. J. Markow, a 24-year-old farmer from the Archangel territory, was admitted to the clinic 3 November 1873. According to his statement, he came to the capitol for the first time in the summer of 1871, looking for work; while there, he became ill with a stubborn, violent diarrhea which continued for several months and finally weakened him so that he was unable to sit up in bed. In this condition he was sent home where the diarrhea diminished slowly and his general condition improved; yet, in the beginning of 1872, he was still so weak that he was found unfit for military service.

Malaria parasitemias were found in 35% of 520 individuals from a village in Timor, Indonesia. Plasmodium falciparum accounted for 80% of infections. The existence of P. ovale in Timor is reported for the first time. The WHO Standard Field Test for drug resistance did not reveal significant resistance of P. falciparum or P. vivax to chloroquine.

With strict adherence to ethical guidelines, a volunteer was immunized against sporozoites of Plasmodium falciparum and P. vivax, the antigen consisting of attenuated sporozoites of each species inoculated through bites of mosquitoes X-irradiated at a minimum dosage of 15,000 rads. On one occasion this dosage did not render all P. vivax sporozoites noninfective. Species specificity of antigen and antibody was demonstrated, but within each species a wide geographical diversity of strains proved interchangeably antigenic and susceptible to the antibody. Once immunized, the volunteer was protected for not more than 3 months and 6 months, respectively, from infective P. falciparum and P. vivax sporozoites, the duration of protection being reflected by a positive species-specific circumsporozoite reaction. Studies in this volunteer, and in two others immunized with P. falciparum sporozoites, did not reveal any increase in serum levels of immunoglobulins G and M.

Four surveys of malaria endemicity were conducted in the Cuiabá Sector of Mato Grosso State, Brazil, at 6-month intervals during the period April 1970 to September 1971; during April 1970 a survey was also conducted in the Campo Grande Sector. Over 4,000 dual specimens—blood films for parasite diagnosis and filter paper blood spots for determination of fluorescent antibody (IFA) response—were collected from the general population, including school populations whenever possible. Parasitologic examinations yielded positivity rates ranging from 0.8 to 2.3%. In the Cuiabá Sector, sero-positives (⩾1 : 20) ranged from 9.3 to 13.6%; in the survey in the Campo Grande Sector only 4.3% of the specimens were positive. There was an expected increase in IFA response with age in both the proportion of positives and mean maximum titers. In the Cuiabá surveys 75 to 91% of the maximum positive responses were to the Plasmodium falciparum antigen, while in Campo Grande only 46% of the maximum titers were for P. falciparum. The wide differences in malaria endemicity observed within the Cuiabá Sector were attributed to differences in climate, geography, and degree of development of the several regions. A study of surveillance reports from 1966 through the survey dates revealed that the high rates of infection seen often resulted from detection activities in the larger cities and probably represented cases imported from endemic areas to the north and west. In order to interpret accurtely the endemicity of malaria in an area and, thus, determine the necessity for introduction or continuation of control measures, thorough epidemiologic studies are necessary. The addition of a serologic method to normal surveillance can increase the accuracy of interpretation.

Sera from individuals infected with Plasmodium vivax were tested for the presence of malarial antibodies using the indirect fluorescent antibody (IFA) and the indirect hemagglutination (IHA) tests. The primary infection resulted in the conversion of all sera to a positive response in the IFA test, whereas only 50% gave a positive IHA response. There was a direct relationship between the duration of the primary parasitemia and percentage giving positive IHA response. Relapse resulted in high level positive IFA and IHA responses.

Soluble antigens were prepared from Plasmodium falciparum and P. vivax and were evaluated in the indirect hemagglutination test. These antigens, attached to aldehyde-fixed type “O” erythrocytes, detected antibodies in more than 91% of infections with the homologous Plasmodium species. Detection rates in infections caused by the heterologous species ranged from 72% to 76%. Positive reactions occurred in less than 2% of sera from persons without malaria infection.

In a study of antigens and antibodies found in malarious chicken blood, antigen activity was found in plasma, and in hypertonic saline eluates of blood cells. A soluble antigen was extracted from parasites liberated from erythrocytes. Two classes fo antigen were differentiated, one a globulin associated “serum antigen” which was found to show identity with a serum antigen from blood of rats with acute Babesia rodhaini infection, and another that was associated with the Plasmodium gallinaceum parasite. The plasma also contained antibody to both classes of antigen. Study of blood cells from normal chickens made anemic by injections of autohemagglutinin-free malarious plasma indicated that both serum antigen and its antibody were present in eluates of the washed blood cells. Direct immunofluorescent tests of these cells with conjugated antibody to serum antigen, and with conjugated antibody to P. gallinaceum parasite antigen showed that they reacted with the antibody to serum antigen but gave no reaction with antibody to parasite antigen. From this information it is suggested that soluble complexes of serum antigen and its antibody combined with the erythrocytes, and that these complexes acted as opsonin to cause the cells to be sequestered and destroyed in the spleen, or may have fixed complement to cause intravascular hemolysis. The serologic identity of serum antigen from malarious chickens and from rats with babesiosis, and its distinction from parasite antigen, led to the speculation that it might be an autoantigenic macroglobulin.

Study of urinary waste of chickens with acute Plasmodium gallinaceum malaria indicated that serum proteins of the globulin and albumin classes were passed. Protein extravasation did not begin until globulin-associated serum antigen and its antibody were detected in the blood. Both serum antigen and antibody were found in the wastes for as long as the antigen was present in the blood. Extracts of kidney tissues contained serum proteins that were not present in extracts from normal kidneys, and serum antigen and its antibody were both present. Frozen kidney sections reacted strongly with fluorescein-conjugated antibody to serum antigen, showing diffuse granular immunofluorescence characteristic of immune complex nephritis. Sections from chickens with nephritis induced by injections of malarious plasma also showed deposits of extravasated antigen. The experiments suggested that complexes of serum antigen and antibody served as a permeability factor, or activated other permeability factors and may have caused the glomerulonephritis associated with acute avian malaria. The passing of serum proteins in the urinary wastes after chickens had recovered from acute malaria suggested that persisting damage may have resulted.

Toxoplasma oocysts in cat feces were marked with a tracer amount of strontium-85 (85-SR), and were superficially buried simulating the natural disposal of feces by cats. Oocyst infectivity in Costa Rica was followed qualitatively and persisted for 1 year in three shaded sites, two moist, and one relatively dry site. Oocyst infectivity was quantitated in the Kansas deposit over a period of 18 months, including two winters. After initial mixing in soil, the level of infectivity remained fairly stable. Infectivity was recovered, probably from the surface of one Musca, serveral isopods, and earthworms. These data on persistence of Toxoplasma oocysts in soil support the concept that Toxoplasma infectivity in nature may be increased logarithmically by cats.

Guinea worm disease is endemic in West Africa. In 1973 a field drug trial was conducted to compare effectiveness, cost, and side-effects of thiabendazole and metronidazole in treating active guinea worm disease and preventing latent worms from emerging. A mass chemotherapy campaign was planned to follow the drug trial. Only 15.5% of the treated patients expelled the worm completely, and in 28.4% of the cases worms continued to appear. Both drugs were equally unsatisfactory in their anti-helminthic effect. Consequently, our efforts to control guinea worm have shifted from chemotherapy to chemical control of cyclops and improvement of rural water supplies.

A study of the epidemiologic characteristics of 125 cases of eosinophilic meningitis or meningoencephalitis, probably caused by Angiostrongylus cantonensis, which occurred in southern Taiwan in 1968 and 1969 revealed a close association of the disease with the rainy season. In contrast to findings in other geographic areas, most such cases in this study occurred among children. A higher attack rate was observed among aborigines than among descendants of mainland Chinese. Most patients had eaten the giant African snail, Achatina fulica, prior to their illness and this mollusc was commonly found infected with third-stage larvae of A. cantonensis. However, in almost all instances the snail was eaten after it had been thoroughly cooked and examination of cooked snail meat revealed only dead larvae. It it suspected that patients became infected by inadvertently ingesting A. cantonensis larvae liberated when the snails were prepared for consumption.

The specificity and sensitivity of adult and larval somatic antigens, and perienteric fluid of Toxocara canis and Ascaris suum were investigated by using intradermal skin tests in guinea pigs. These animals were infected with low doses (0.01, 0.1 or 1.0 egg/g) of these helminths. Toxocara larval antigen (TL) induced larger reactions in Toxocara-infected animals than did the other antigens, suggesting a superior sensitivity for this antigen. In addition, Ascaris perienteric fluid (AP) provoked skin responses in these animals of a magnitude similar to those induced by TL. The reciprocal relationship, i.e., comparable reactivity of AP and TL in Ascaris-infected animals, was not apparent. In general, Ascaris larval antigen and AP elicited larger intradermal reactions than other antigens in Ascaris-infected animals. The results of this study indicated no superiority of adult antigens in differentiating Ascaris and Toxocara infections.

The specificity and sensitivity of adult and larval somatic antigens and perienteric fluid of Toxocara canis and Ascaris suum were investigated by using a modified passive cutaneous anaphylaxis procedure in guinea pigs. Pooled sera from animals infected with low doses (0.01, 0.1, or 1.0 egg/g) were most reactive with the homologous larval antigen preparation. However, the Toxocara antisera were highly reactive with this antigen only, whereas the Ascaris antisera reactions could not be interpreted as being clearly positive with any of the antigen preparations. Sera from hyperinfected animals were also reactive with the homologous larval antigen. In addition, Ascaris larval antigen was reactive with Toxocara antiserum. The reciprocal relationship, i.e., reactivity of Toxocara larval antigen with Ascaris antiserum, was not apparent. In no instance did adult antigens induce reactions that could be interpreted as specific or sensitive indicators of antibody.

Serum samples from ten children with visceral larva migrans were evaluated by analysis of: immunoglobulin concentrations, precipitin reactions against Toxocara and Ascaris antigens and blood group substances, and IgM and IgG activity against Ascaris antigen by radioimmunoassay (RIA). The elevated concentrations of serum IgE and IgG and the positive precipitin reactions which occurred in some cases are an aid in diagnosis but were not consistently present. Serum IgM concentrations were elevated in all cases. IgM or IgG antibodies against Ascaris suum antigen were detected in all cases by a solid phase RIA technique. Radioimmunoassay techniques of this type may provide a superior method of diagnosis, particularly if used with serial serum samples which demonstrate changing levels of antibodies.

A case of mycetoma of the mandible caused by Madurella mycetomii is reported. Diagnosis was established by culture, histopathology and serology.

Patients with borderline-lepromatous (BL) or fully lepromatous (LL) leprosy were treated in the sanitarium for approximately 1 year with oral rifampin (600 mg daily) or with oral dapsone (100 mg daily). They were then treated as outpatients with intramuscular acedapsone (225 mg every 12 weeks) or oral dapsone (50 mg daily). They have now been followed for a total of 28 to 34 months. Death of Mycobacterium leprae during the initial 24 weeks was monitored by mouse inoculation with M. leprae from skin punch biopsy specimens. With rifampin therapy, death of M. leprae occurred rapidly, and viable M. leprae were nearly undetectable by the time the first specimen was taken after the start of treatment, at 4 weeks. With dapsone therapy, death of M. leprae was slower, and in some cases the inoculation results were still positive at 12 weeks. The therapeutic response during the period of outpatient treatment has been satisfactory. The number of dead M. leprae, as measured by the bacterial index in skin smears and the number of acid-fast bacteria in skin specimens, has continued to decrease, and clinical progress has been satisfactory. The measured drug-induced death of M. leprae occurred at about the same rate in BL patients as in LL patients. Disappearance of dead M. leprae from the tissues was much more rapid in BL patients than in LL patients.

Acedapsone (DADDS), a repository sulfone given by injection five times a year, has been used since 1967 for the treatment of all leprosy patients in the Karimui, an area of difficult access. More than 460 patients have been treated, 336 beginning in November 1967 and continuing through the latest assessment 6 years later. The injections have been well received and they have been administered very regularly. Clinical observations were begun before 1967, so a base-line of assessments was available for the patients whose disease appeared before that time. The response to DADDS therapy has been satisfactory except in 5 of the 28 multibacillary patients in whose smears solid-staining Mycobacterium leprae have reappeared. M. leprae was isolated in mice from three of these patients; one strain has been proven to be completely susceptible to dapsone (DDS), and the other two very probably are. DDS levels in the plasma of these five patients were normal and well above the minimal inhibitory concentration. The most probable explanation is that a few viable M. leprae survived in the presence of inhibitory concentrations of DDS for the 4 to 6 years during which dead bacilli were disintegrating and disappearing from the tissues. The other 23 multibacillary patients responded satisfactorily. The decrease in the number of M. leprae in the skin smears has been most prompt in patients with low initial bacterial loads and in those with borderline lepromatous diagnoses. A high initial bacterial load and a fully lepromatous diagnosis were associated with a slow initial loss of M. leprae in the 1st year, followed by a more rapid loss the next year. All of the multibacillary patients have now been treated by the addition of a 90-day course of rifampicin.

Skin testing with antigens from Histoplasma capsulatum, Mycobacterium tuberculosis (PPD-S), and atypical mycobacteria (PPD-B, PPD-G, PPD-Y, and PPD-platy) was carried out among six population groups in the Solomon Islands between 1968 and 1972. There was no positive reaction to histoplasmin among any of the groups, suggesting that histoplasmosis is not endemic in the Solomon Islands. There were significant numbers of tuberculin reactors among each group. Largest mean reactions to PPD-S were present among the Lau and Ulawa, in whom reactions to PPD-S were larger than those to any other antigen tested. Thus significant infection with M. tuberculosis appears to occur in these populations. This was corroborated by radiologic survey. Among the Lau, large reactions to PPD-G and PPD-Y were also elicited, raising the possibility of multiple infection. Among the Aita, Baegu, Nagovisi, and Ontong Java, PPD-G elicited the largest reactions. PPD-G produced the second largest reactions among the Lau and Ulawa. PPD-S elicited the largest or second largest reaction among 4 of the 6 groups. A notable exception was the Aita, in whom PPD-S elicited the smallest mean reaction. The Aita also had the lowest prevalence of radiologic findings consistent with tuberculosis. These observations suggest that M. tuberculosis has been introduced into the Solomon Islands from outside sources, a hypothesis which may explain the variability in prevalence of tuberculosis-like disease demonstrated by chest film among the six groups. Genetic differences may also play a role in this variability. The study also demonstrated a high prevalence of “baseline” sensitivity to the atypical mycobacteria among the Solomon Islanders. This sensitivity may confer some immunity to infection with M. tuberculosis, but this protection is far from complete.

Rates of trachoma infection of family members were compared for two groups of index cases; all were infants about 1 year old observed over a period of several months in a previous study. Group A infants were consistently infected with trachoma, and Group B infants were not infected with trachoma. On the average, 50% of Group A family members had active infection (as determined by trachoma inclusions in their conjunctival cells) and 80% of the siblings within 6 years of age to the index cases were infected. Only 9% of Group B family members had active trachoma, and 20% of the siblings within 6 years of age to the index case were infected. This study suggests intrafamilial spread of trachoma.