The American Journal of Tropical Medicine and Hygiene - Volume 13, Issue 1, 1964

Using the indirect fluorescent antibody method, the production and persistence of specific antibody was demonstrated in three patients inoculated with blood parasites of Plasmodium malariae. In one case a relatively high antibody level was maintained in association with persistent asymptomatic parasitemia, while in one of the others, termination of the infection resulted in a delayed, slow decline in antibody titer to a persistent lower level. Higher antibody titer appeared to be associated with the primary infection characterized by reduced parasitemia and febrile attack.

Direct staining of Plasmodium berghei with fluorescein-labeled antiserum from infected rodents indicated that these animals are capable of producing an antibody against the parasite. A naturally occurring P. berghei-antibody complex was detected by exposing parasitized erythrocytes from infected mice to fluoresceinlabeled anti-mouse globulin.

A modified procedure for the examination of reduviid bugs used in the xenodiagnosis of infection with Trypanosoma cruzi is described. It consists in the homogenization of a group of test insects in saline solution and the subsequent filtration, centrifugation and phase-contrast examination of the sediment for trypanosomes. The advantages of this modified procedure are its greater rapidity, simplicity and sensitivity compared with the older method. This xenodiagnostic procedure is recommended especially for epidemio-parasitological surveys and for routine parasitological examinations in individuals with latent or chronic infection with T. cruzi.

Strains of Trichomonas vaginalis were isolated from symptomatic patients and normal persons and injected into groups of mice via the intraperitoneal, subcutaneous and intramuscular routes. No relationship was found between the human host status and the virulence of the strain for mice injected intraperitoneally. A possible relationship was observed in mice injected subcutaneously in that the majority of strains isolated from symptomatic patients exhibited more marked virulence for mice than did any of the strains isolated from normal persons. The intramuscular route did not yield data of any value in assessing a possible relationship.

There is a close correlation between radiocardiographic picture, pulmonary circulation time (PCT), and the clinico-radiologic grades of bilharzial cor pulmonale. In grade I both PCT and radiocardiogram were normal. On the other hand, radiocardiography in cases of grade II revealed an increase in the duration of the descending limb of the R wave as well as moderate prolongation of PCT. Lastly, grade III was characterized by marked prolongation of PCT, together with a large R wave in the radiocardiogram due to prolongation of both the ascending and descending limbs of this wave.

As an extension of laboratory studies in experimental animals a 15-month study was conducted in Puerto Rico on the effects of improving the nutrition of malnourished people infected with Schistosoma mansoni. At the beginning and at intervals during the study the patients were hospitalized for brief periods for extensive laboratory and clinical examinations. After they were provided an enriched diet for 9 months some were cured by stibophen therapy and the effects of treatment were observed for an additional 6 months. A group of similarly malnourished individuals were studied as controls.

Evaluation of the results of the study led to the following conclusions:

Nutritional inadequacies of the usual diet of the people studied included (a) protein, especially of animal origin, (b) ascorbic acid, (c) riboflavin, (d) niacin, and (e) calories.

All patients had a history of more or less ill health characterized by excessive fatigue, aching, anorexia, stomach discomfort, frequent colds and chills, and underweight. After the enriched diet was provided, marked improvement in the health of the patients was observed.

A regimen of stibophen therapy devised for this study (0.5 mg stibophen per kg body weight twice daily for 10 days) resulted in cures in every case without accompanying severe side effects. Following treatment the malnourished individuals in the control group showed improvement in respect to liver function, erythrocyte sedimentation rate, weight gain and general health. Further improvement of the health of individuals in the enriched-diet group following treatment was also observed.

Serological tests using fluorescent antibody, slide flocculation, complement-fixation and circumoval precipitin techniques remained reactive at high titers in most cases up to the end of the observation period, 10 months after treatment was completed. No difference in diet effect could be detected.

The results of egg counts on patients receiving the enriched diet were inconclusive. In some cases there was an apparent increase while in others either no change or a decrease. Fluctuations in the number of eggs passed, however, were sufficiently great to make interpretation difficult or impossible.

A miracidia-immobilizing substance has been demonstrated in tissue extracts of the snail Australorbis glabratus subsequent to infection with Schistosoma mansoni. Detection of the immobilizing substance in snail extracts occurred as early as 9 days postinfection. The immobilizing activity of the extracts was not diminished by brief periods of freezing, storage at 5°C, or heating to 56°C for 30 minutes. Absorption of up to 67% of the immobilizing activity of the extracts could be accomplished by exposure to either living or formalin-fixed cercariae. With two exceptions, extracts prepared from other species of snails refractory to S. mansoni infection gave no evidence that immobilizing substances were present.

Twenty-three cases of human sparganosis are reported. Of these, 21 were in residents of the southern United States, principally Louisiana, Texas and Florida. Two infections were in patients from Puerto Rico and British Honduras. Cases of sparganosis have been diagnosed annually since 1953, and except for two that were seen in 1948 and 1949, also reported herein, the infection had not been observed previously in Louisiana. With the addition of these 21 cases, the total number of naturally acquired infections reported for the United States to date is 35, of which 25 occurred in residents of Louisiana and adjoining states.

A preliminary survey of porcine cysticercosis was conducted at a large abattoir in each of the five countries in Central America and in Panama during a 3-year period. Over one-half million swine were slaughtered at the six abattoirs. The number of animals condemned for cysticercosis was 11,628 and for all causes 17,100. Sixty-eight percent of the condemned hogs had cysticercosis. The prevalence of porcine cysticercosis in these Latin American countries ranged from 1.75 to 2.78 percent. The economic loss from cysticercosis in these six abattoirs alone exceeded one-half million dollars. Data on the prevalence of human intestinal cestodiases in Guatemala and of human cysticercosis in Guatemala and El Salvador are presented for correlative purposes. The magnitude of the problem of porcine cysticercosis in Central America and Panama is such that it has significant economic, nutritional and medical impact in this area.

Stilbazium iodide (Monopar®) in doses of 8.8 mg/kg twice daily for 3 days was effective against Trichuris trichiura and Ascaris lumbricoides. In a group of children given this dosage, 9 of 23 with Trichuris, and 13 of 18 with Ascaris infections were cured. In the above dosage the drug showed only moderate efficacy against Ancylostoma duodenale and Necator americanus. For Ascaris infection, 10 mg/kg given once daily for 3 days was as effective as was the 8.8 mg/kg twice daily schedule. Vomiting was common but no other side-effects were noted.

Experiments were designed to search for mechanisms responsible for the maintenance of stable populations of microfilariae. Brugia pahangi and Dirofilaria immitis infections in dogs were chosen for the study. Results of experiments showed that: (1) Microfilariae transfused into uninfected dogs circulated for several weeks. The rate of recovery was greatest in a splenectomized recipient and least in a dog to which a transplanted adult worm had been given. (2) Splenectomy had no effect on the levels of microfilaremia in dogs infected with D. immitis. (3) Neither the addition of microfilariae (by transfusion) nor the removal of microfilariae (by withdrawal of large quantities of blood) caused any permanent alteration of the original levels of microfilaremia. Though the exact controlling mechanism(s) remains obscure, this study supports the view that the maintenance of stable populations of microfilariae is a manifestation of successful inter-adaptation between the filarial parasite and its host.

This portion of the studies on microfilaremia in dogs was concerned chiefly with the immunologic response of uninfected dogs to repeated injections of living microfilariae concentrated by a newly devised technique employing phytohemagglutinin. Immunity in these dogs was demonstrated by in vitro tests with living microfilariae, by passive transfer of their sera, and by the effects of the sera on the production of microfilariae by adult worms maintained in vitro. Uninfected dogs that received multiple immunizing inoculations of microfilariae tolerated no circulating microfilariae regardless of the size of the challenge inoculum. Sera taken from these dogs agglutinated homologous, living microfilariae, whereas no agglutination took place in sera from control dogs or from infected dogs with patent microfilaremia. Absorption tests indicated that these agglutinins were specific. The production of microfilariae was inhibited when such sera were incorporated in media used for the in vitro maintenance of adult worms. Furthermore, when serum from “immunized” dogs was injected intravenously into infected dogs, the levels of microfilaremia in the latter animals were significantly lowered. These observations suggest that the antibody demonstrated in vitro is also effective in vivo.

It was inferred from these results that a relationship exists between the levels of microfilaremia and the concentration of specific antibodies produced by the host in response to the presence of microfilariae, and that a high titer of such antibodies is probably responsible for the absence of a microfilaremia in some filarial diseases.

Data are presented on a heretofore unstudied, rather isolated village in southeast Taiwan. It was found that the prevalence of hookworm was significantly lower among the aborigines in the area than it is among the people on the western plains of Taiwan. Ascaris lumbricoides, Trichuris trichiura and hookworm rates indicated no unusual relationship with respect to sex or age.

Comparison by ethnic groups did not indicate any significant differences between Taiwanese and aborigines in the infection rates of A. lumbricoides, T. trichiura, or hookworm. Hymenolepis nana was found in aborigines only. Intestinal parasites were found in 82% of 87 aborigines and 85% of 52 Taiwanese.

Puerto Rican patients reacted to helminth skin test antigens with significantly enhanced reactions to various specific and nonspecific antigens as compared with patients born in the United States. An adult hospitalized group of 347 tubercular patients in New York City was skintested with four helminth antigens. In this group, 233 were native-born Americans, 26 foreign-born but of long residence in the United States, and 88 Puerto Ricans. All individuals were tested with antigens prepared from adult worms of Angiostrongylus cantonensis, Dirofilaria immitis, Schistosoma mansoni and larvae of Trichinella spiralis and with a control. Among the 259 non-Puerto Ricans, none reacted to the A. cantonensis antigen, 3 to the D. immitis antigen, 9 to the T. spiralis antigen and 2 to the S. mansoni antigen. Among the 88 Puerto Rican patients 16 reacted to the A. cantonensis antigen, 10 to the D. immitis antigen, 9 to the T. spiralis antigen and 24 to the S. mansoni antigen. The epidemiologic importance of evaluating nematode skin test antigens in carefully selected control population groups is discussed.

The clinical, epidemiological and laboratory aspects of the first confirmed case of human melioidosis reported in Ecuador are presented. The results of conventional bacteriological and serological testing and of animal inoculation confirmed the presumptive diagnosis of infection with Pseudomonas pseudomallei made by the fluorescent antibody test. Specifically stained fluorescent organisms were demonstrated in tissue impression smears prepared from the organs of guinea pigs experimentally infected with the specimen cultures. The value of immunofluorescence for screening of specimens was emphasized by the rapidity with which Pasteurella pestis and P. tularensis were excluded from consideration as probable etiologic agents of this infection and the short period of time required to make a presumptive identification of Ps. pseudomallei. The role of fluorescent antibody procedures in bacteriological and histopathological laboratories is discussed. A procedure for minimizing erroneous diagnoses of melioidosis is proposed.

A comparison of the serological responses to several cholera vaccines and vaccine regimens has been conducted in groups of people in the Philippines. Responses to the vaccines and vaccine regimens, as determined by agglutination and vibriocidal antibody titrations, were observed to differ depending on the vaccine and dosage employed. Those vaccines which were most potent in active mouse protection assays elicited the best responses in the human subjects. Single doses of suitable vaccines were found to give nearly 100% serological response in small groups of individuals. Tests on a vaccine composed of El Tor vibrios showed it to be a safe and potent antigen in humans. It is recommended that consideration be given to the inclusion of El Tor vibrios in cholera vaccines for general use, although locally, in outbreaks of El Tor cholera, exclusive use of an El Tor vaccine would seem justified by the results of this investigation.

Clinical and virological studies of a case of Apeu arthropod-borne virus infection acquired in the laboratory are described. The virus was isolated from the patient's acute phase serum and was identified by serological methods. Relation of the viral isolate to the illness was supported by development of hemagglutination-inhibiting, complement-fixing, neutralizing and precipitating antibodies to Apeu virus in the patient's convalescent serum.

A previously undescribed agent has been isolated from Trichoprosopon mosquitoes captured in the Arena Forest in central Trinidad. The name Triniti virus is proposed for this agent. Neutralizing antibody to the virus has been demonstrated in human serum. Some of the physical and biological properties of the virus are described.

This report describes the isolation and partial characterization of a virus from soft ticks which had been collected on Bush Key, Dry Tortugas, Florida, and provisionally identified as Ornithodoros capensis Neumann, 1901. Another virus which appears to be similar or identical to the Dry Tortugas isolate was recovered from a pool of ticks of the same species collected under rocks near nesting gulls and terns on Raza Island, Gulf of Baja California, Mexico.

Infection was produced in Swiss mice, house mice, hamsters, guinea pigs, a rhesus monkey, and chick embryos by at least one route of inoculation. In all mice and suckling hamsters, significant histopathologic changes were present only in the central nervous system.

The Dry Tortugas agent has been passed through filters of various pore sizes and appears to be about 100 mµ in diameter. It is sensitive to both ethyl-ether and sodium desoxycholate.

Mouse brain and serum antigens were tested for ability to hemagglutinate and the results were negative. These same antigens failed to react in either complement-fixation or neutralization tests with any of the antisera that were available, including that prepared against several other tick isolates. Therefore, this agent probably represents an undescribed virus.

Seven strains of virus were isolated from two species of mosquitoes, Culiseta melanura and Culex pipiens, and from the spleen of an ovenbird (Seiurus aurocapillus) collected near the town of Flanders in Suffolk County in southeastern New York State. These strains belong to the same antigenic group and appear to be related to the arbovirus strains called Hart Park and WS 1087 isolated from Culex tarsalis collected in southwestern United States.