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

An improved antigen for the complement fixation test was prepared by extracting desiccated, cultured T. cruzi with anhydrous ether in the cold (-15° to -18° C.) prior to final extraction with alkaline buffer. Preliminary extraction with ether markedly reduced the tendency of the antigen to react with sera from syphilitic and healthy individuals, and had no appreciable effect upon its capacity to react specifically with antibody produced in American trypanosomiasis (Chagas' disease).

Persons infected with L. brasiliensis could not be differentiated from individuals with American trypanosomiasis on the basis of their serologic reactions with T. cruzi antigen.

Using the Sabin-Feldman “dye test”, 987 sera from the rural, Negro population of Fayette County, Tennessee, were tested for antitoxoplasmic antibodies. The following conclusions were established:

• 1.  There is no significant difference between the sexes at any age with regard to anti-toxoplasmic antibodies.
• 2.  With the exception of the youngest age group, the percentage of positive titers in the population increases with age.
• 3.  There is a highly significant shift of modal titer, from positive at a dilution of 1:64 or higher in persons under 20 years of age to 1:16 or less in persons 20 years of age or more.
• 4.  Considerable evidence can be seen of a bimodal distribution of titers, with an abnormally large number of undiluted positive sera.
• 5.  When the data for each age group are standardized to the actual census population, the overall prevalence of positive reactors is 29.9 per cent for all positive titers, and 21.8 per cent for titers of 1:16 or higher.

Of 15 cases of sleeping sickness treated with Puromycin, 5 relapsed and 10 were free of infection, clinically and parasitologically, 25 months after treatment. No other specific drug was administered at any time to any of the 10 patients who did not relapee.

The incidence of Trichomonas vaginalis in a group of 301 normal Negro women aged 20 to 81 years was 12.3 per cent and 14.8 per cent for those between the ages of 20 and 49 years. For the respective groups of normal white women the percentage incidence was 2.9 and 3.5.

The frequency of infection in women of the Negro group who have passed the menopause (60 years and over) was relatively high in the Negro group though lower than in the younger women. Of 93 normal Negro women examined 9 were positive, while 2 of 214 normal white patients harbored the flagellate. The incidence of infection was found to be higher among patients with symptoms.

No trichomonads could be demonstrated in a series of Negro newborns aged 1 to 5 days. The incidence of infection in normal Negro females 1 to 9 years old and between the ages of 10 and 19 years (actual age range 12–17 years) was 3.6 per cent and 18.9 per cent respectively.

Clinical poliomyelitis is uncommon in the native population of Liberia, but is relatively much more frequent in foreign visitors. The serum neutralization test against poliomyelitis viruses was performed, using the serum of 80 Liberians of various ages, and indicated a rapid accumulation of sero-immunity, up to an average level of about 90 per cent by 5–6 years of age. This pattern of sero-immunity is very comparable to the patterns found in other studies of under-sanitated areas, and indicates an abundance of poliovirus and infection at a very early age.

The pattern of sero-immunity in Liberia is markedly different from that in an American city studied by Melnick and Ledinko and perhaps typical of the population of foreigners in Liberia. This suggests that the foreign adult visitors may include a significant number of non-immunes who are at hazard in an under-sanitated area. The use of prophylactic vaccination against poliomyelitis is not now justified in the native Liberian population, but may be in the foreign visitor to Liberia.

During the course of investigation to determine the vector of sylvan yellow fever in Honduras, an unidentified neurotropic virus was isolated from mosquitoes of the genus Psorophora (Rodaniche, 1956). On the basis of cross-immunity and neutralization tests it was determined that this virus was not that of yellow fever. Unfortunately, other appropriate virus strains or immune serums were not available here for making a final classification. However, Dr. Jordi Casals, of the Rockefeller Institute, generously offered to carry out systematic immunological studies with a pooled mouse hyper-immune serum forwarded to his laboratory, and found the virus to be “identical with or closely related to Ilhéus.” Animal pathogenicity and other properties of the Honduran strain as observed in this laboratory also conform to those of Ilhéus.

The virus of Ilhéus encephalitis was isolated for the first time in 1944 by Laemmert and Hughes (1947) from a pool of mosquitoes of the genera Aedes and Psorophora captured in the vicinity of Ilhéus in the State of Baia, Brazil.

Aedes sollicitans mosquitoes became infected with Eastern equine encephalitis (EEE) from feeding upon an inoculated horse. These mosquitoes, after two weeks' incubation, transmitted infection by bite to a normal horse. Attempts to infect more mosquitoes by permitting them to feed upon this second horse met with failure. The virus which circulated in the blood of the inoculated horse titered as high as 10-5.5, a level not commonly attained in horses. The horse infected by mosquito bite had a lower, more usual concentration of virus in its blood, inadequate to infect mosquitoes. The results of these studies prove it possible for an occasional horse to serve as an EEE infection source for mosquitoes. It is believed, however, that horses rarely play an important role in EEE propagation.

From this observation it appears that dengue fever virus (Hawaii mouse adapted) may be transmitted from lactating hamsters to suckling hamsters. None of the mothers showed symptoms of nervous system involvement over a 21 day observation period. Mouse tests of their brains were negative. Four out of 32 suckling hamsters developed symptoms of nervous system involvement and their brains were shown to contain dengue fever virus by neutralization tests conducted intracerebrally in Swiss albino mice. The control sucklings and sucklings from the exposed mothers showing no signs of central nervous system involvement were sacrificed and their brains tested by the intracerebral mouse test, but no virus was demonstrated.

The incidence and etiology of diarrheal disease in a group of 55 Egyptian village adults were studied by weekly clinical, bacteriological and parasitological observations over a period of eight months. There were, on the average, 1.2 episodes of diarrhea per subject during this time, or an estimated annual attack rate of 1,800 cases per 1,000. Shigella or Salmonella were demonstrated in 9 per cent of the episodes. The subjects were heavily parasitized with E. histolytica, A. lumbricoides and S. mansoni but it was difficult to associate the presence of these parasites with the diarrheal episodes.

Adults were infected with Shigella at about the same frequency as children living in the same environment, but a far greater percentage of the infections in adults were asymptomatic with respect to diarrhea. This suggests that, under constant exposure, susceptibility to infection with Shigella decreases with age.

A number of conditions which may influence the survival of the fly were studied under experimental laboratory conditions. One feeding a day of milk and sucrose was found to be sufficient for maintaining the flies. Water, when offered, was rejected most of the time and did not significantly increase the survival time (ET50). Caged flies under normal insectary conditions lived considerably longer than did immobilized test flies.

In general, multiplication of E. coli did not appear to take place in the insect's alimentary canal. Somewhat over 50 per cent of the bacteria ingested were recovered. There was no significant difference in bacterial output by the flies fed on diets containing different amounts of sucrose in skim milk, although this would have had to be great in order to be significant because of the variations in the total counts within the diets. Almost all the bacteria were released by the time of the ET50.

E. coli was tagged with radioactive P32 and fed to the flies. For several days thereafter there was fairly good correlation between the radioactive and bacterial counts.

The flies' rate of uptake of E. coli was determined under laboratory conditions. The maximum number of bacteria was found after 45 to 60 minutes. Following this, there was an apparent decrease for approximately 5 hours; then there was an apparent increase, indicating a revisit by the fly to the source of the organisms.

A procedure is described for the determination of the egg producing capacity of female schistosomes from the time of maturation to the termination of infection. Using this procedure the comparative egg producing capacities of female S. mansoni and S. japonicum were studied in the hamster and information obtained on the relative distribution of eggs in the feces and in the various tissues and organs.

Each female of S. mansoni produced an average of 300 eggs per day within the period under study. Only 22 per cent of all eggs produced were passed in the feces; 18 per cent remained in the wall of the large intestine; 32 per cent in the small intestine; 26 per cent in the liver; and 2 per cent in the mesenteries and its associated lymph nodes and pancreas. The percentage of eggs found in the spleen and lungs was small and numerically insignificant.

Each female S. japonicum produced an average of 3500 eggs per day. Only 16 per cent of all eggs produced were passed in the feces; 50 per cent were found in the wall of the large intestine; 10 per cent in the small intestine; 23 per cent in the liver and 17 per cent in the mesenteries, associated lymph glands and pancreas. As in the S. mansoni infections, the percentage of eggs found in the spleen and lungs was small and insignificant.

Forty-nine recent or old cases of schistosome dermatitis which occurred mainly in the vicinity of Douglas Lake, Michigan, were tested intradermally with the worm antigen of S. japonicum and cercarial antigen of S. mansoni. At the same time the antigens were tested intradermally on 49 cases that had had no history of schistosome dermatitis; and the results were negative.

It is concluded that schistosome dermatitis cases, caused by the penetration of the cercariae of avian schistosomes, seldom give positive intradermal reactions to the antigens made from the human schistosomes, S. japonicum or S. mansoni, due probably to a limited antibody production. A differential diagnosis between schistosome dermatitis and seabather's eruption of non-schistosome origin can not be made adequately by an intradermal test with human schistosome antigen. The results of the present study also indicate that the use of intradermal antigens for diagnosis of human schistosomiasis is valid even in the areas where the people may well have been exposed to avian schistosome cercariae.

Cytochemical studies on the hepatic lesions of DD mice infected with Schistosoma japonicum gave additional evidences of hepatic damage, in which significant findings were a marked increase of glycogen and fat, and a decrease of RNA in the cytoplasm of hepatic cells together with the frequent occurrence of nuclear karyorrhexis. In addition, there was the excessive accumulation of acid mucopolysaccharides (hyaluronic acid type) in the connective tissue of schistosomal granuloma and in the walls of portal vessels. The possible effect of these substances was considered to be the induction of the circulation disturbance in parenchymal tissues rather than the toxic effect of schistosomal worms or eggs. The flame-like, eosinophilic deposits about the schistosomal eggs were composed of polysaccharides other than glycogen and closely related to the substance of the egg shell. The hemosiderin-like pigment deposited in the enlarged, Kupffer cells showed a marked affinity with silver and the lack of evidence for the presence of ferric, ferrous and masked iron. Only one of a number of dissolving agents for the pigment was 40 per cent alcohol sulfate. Considering the results of many cytochemical tests, the best possible suggestion for its nature was its analogy to melanine rather than to products of hemosiderin decomposition.

The adult worms of Schistosoma mansoni live in the veins of the portal system, mainly in the radicles of the inferior mesenteric vein. The eggs are deposited in the venules of the submucosa in the large bowel and escape through the mucosa into the intestinal lumen, mixing with the feces. However, many eggs do not reach the intestinal lumen but are retained in the intestinal wall itself or may spread to many organs or tissues not related to the portal venous system, i.e., lungs, central nervous system, heart, kidneys, thyroid, etc. (Faust, 1948; Maciel et al., 1954; Lichtenberg, 1955). The eggs reach the lungs through the hemorrhoidal plexus, a communication between the portal and systemic venous systems (Mainzer, 1951). The frequent liver cirrhosis in schistosomiasis widens that communication. The routes of dissemination to other organs are not known and many theories have been adduced.

A case of immune thrombocytopenic purpura due to Fuadin has been reported. The reaction occurred on 2 occasions when the drug was given. Administration of plasma from this patient to a recipient who also received Fuadin produced thrombocytopenia without purpura. It is postulated that thrombocytopenic purpura in this patient was due to the occurrence of a drug-antibody complex capable of destroying or agglutinating platelets and depressing megakaryocyte activity.

Moose, elk, caribou and reindeer have been recorded with hydatid cysts, and wolves with the adult tapeworm in Northwestern Canada. Fresh reindeer hydatid fluid was used to prepare antigen and used in intradermal tests on Indians in Canada's Northwest. The total number of natives tested with this Canadian antigen in two years was 2,022 with 31 per cent giving positive reactions.

The liver was found to be the primary site of infection for Echinococcus alveolaris; however, lung, kidney, spleen, pancreas and alimentary canal were also found to be affected. The acute cellular reaction caused by the infection and the pathological changes produced in the different organs are also described in detail. Perivascular infiltration with mononuclear cells was found to be characteristic of this infection and was observed in liver, lung and kidney. The chief characteristic of the larval stage of E. alveolaris is the type of lesion, which behaves very much like an infiltrating neoplasm.

Single doses of piperazine citrate were administered during mass treatment of human ascariasis in five study areas in the mountains of eastern Kentucky. A total of 282 persons was treated in four groups with three different dosage schedules, two groups receiving a laxative after treatment. In the more successful laxative group, 64 per cent of the individuals had egg counts reduced to zero as determined by observations before and after treatment. However, in another group omitting the laxative, a cure rate of 79 per cent was obtained. Reports of side effects were few and judged to be of little concern. Piperazine citrate in single dosage is considered an effective public health measure for use in control of roundworm infections.

The standardized direct smear and the Stoll dilution egg counting methods were compared in 1,000 fecal samples. Of these 411 had shown A. lumbricoides, 951 T. trichiura, 449 N. americanus and 310 S. mansoni eggs.

The data obtained with the two methods were analyzed by the x2 test and coefficient of correlation. In general the techniques compared favorably. The A. lumbricoides was represented by all degrees of intensity of infection and gave highly significant results. A majority of the infections with the other three helminths were light. It is believed that this led to the less significant results obtained with these species. It is concluded that the standardized smear is the technique of choice.

The remarkable reduction in murine typhus fever in southern United States is generally attributed to large scale control measures, particularly DDT dusting to kill rat fleas. Notwithstanding that such control operations were not in effect in Puerto Rico, the reported rate dropped steadily and there was a 100 per cent decrease in the City of San Juan (137 reported cases in 1944 and none in 1954). In an attempt to explain the decline of this disease a rat ectoparasite study together with human and rat serological surveys were undertaken. Ectoparasite data from 600 rats collected in the City of San Juan from April 15, 1954, through May 4, 1955, when compared with data from 775 rats trapped during the same period in 1946–47 demonstrated that the flea vector, Xenopsylla cheopis, had decreased in population sufficiently to account for the lack of human cases; for only 16 per cent of the rats in 1954–55 were infested with an average of 0.42 specimens per rat as compared with 54 per cent infested and 1.75 specimens per rat in 1946–47. Decrease in flea population was greater in the residential section known as Santurce where only 5 per cent of the rats were infested than in the largely business district, San Juan Islet, where 26 per cent of the rats were still infested. As regards Santurce, data from earlier surveys indicated that there has been a consistent downward trend in rat flea population during the last eight years. Complement-fixation tests on 279 rats resulted in only 3.2 per cent positive at dilutions of 1:8, indicating that infection among rats is negligible. Of 368 human subjects, 3.8 per cent were positive at dilutions of 1:4 or above using the complement-fixation test; since a positive reaction may be given years after recovery and because of very low titers as well as other reasons it is believed that the reported rate is essentially correct and there are few if any unreported cases.

On the basis of this evidence from Puerto Rico it is concluded that a reduced typhus rate is not proof of the efficacy of control operations. Further, it is possible that control was instituted in southern United States after the epidemic had already receded, and that without the large scale control projects there the disease might have followed the same course it has in Puerto Rico. No explanation has yet been found for the decrease in the reproductive potential of rat fleas during the last decade in San Juan, P.R., since rats are abundant and the climate has been favorable for flea development, at least as regards temperature and humidity. Improvements in construction, food storing, general sanitation and mosquito control may have had an incidental effect on rat fleas, but do not account for the great reduction in population which has occurred.