The American Journal of Tropical Medicine and Hygiene - Volume 13, Issue 3, May 1964

I have been honored by this invitation to present the Charles Franklin Craig Lecture. The high quality of these lectures in years past has impressed me. It has also afforded me little peace of mind. I should like to be able to present to you today a striking synthesis of the diagnostics of arbovirus infections, and a chart outlining and clarifying the differential diagnosis of such infections so that one could distinguish them from infections caused by other viruses, protozoans, microbes, fungi and even helminths.

It is disturbing to have to admit that I am quite incapable of presenting such a synthesis. I have been unable, in the past few years, to convince myself that any magic formulae exist which might enable one to arrive at a precise diagnosis in the field of fevers of unknown origin (F.U.O.'s), pyrexias of unknown origin (P.U.O.'s), “cat fever,” “three-day fever,” “five-day fever,” “status febrilis,” “influenza,” aseptic meningitides with and without rash, meningoen-cephalitides, diarrheas of shorter or longer duration, illnesses with jaundice and dengue-like illnesses.

A repository preparation of the dihydrotriazine metabolite of chlorguanide (proguanil), known as CI-501 (Camolar®), was tested in 24 prisoner volunteers for its effectiveness as an antimalarial drug.

The 24 premedicated volunteers were challenged 1 to 10 times by the bites of Anopheles quadrimaculatus mosquitoes heavily infected with the Chesson strain of vivax malaria. As of 24 November 1963, 12 of the 24 volunteers have developed patent infections 169 to 586 days after medication or 13 to 434 days after their last exposure to infection. The remaining 12 volunteers continue to show no evidence of infection 619 to 730 days (20 to 24 months) after medication.

These results indicate that this preparation has the capacity to exert long-term protection against vivax malaria. The importance of such a preparation in a program of world-wide malaria eradication is stressed.

A repository preparation of the dihydrotriazine metabolite of chlorguanide, known as CI-501 (Camolar®), given as a single intramuscular injection at a dose of 5 mg (base) per kg body weight, was tested for its antimalarial activity against Plasmodium falciparum in 14 prisoner volunteers.

The medicated volunteers were exposed to infection with a Southern Rhodesian strain of P. falciparum, either by the intravenous inoculation of parasitized homologous blood and/or by the bites of heavily infected Anopheles freeborni mosquitoes. The number of challenges (i.e., exposures to infection) ranged from 1 to 6. The intervals of time between exposures were variable. Twelve volunteers served as controls to prove the infectivity of the challenges.

Whereas CI-501 did not protect against infection with this strain when the challenge was by trophozoites (parasitized blood), it did protect through a minimum of 383 days against infection when challenges were by the bites of heavily infected mosquitoes. One volunteer, after his sixth exposure at 446 days after medication, developed patent parasitemia on day 458.

These results indicate that CI-501 has the capacity to exert long-term protection against falciparum malaria, as it was previously demonstrated to have for vivax malaria, provided the parasites are sensitive to chlorguanide. Moreover, in the case of falciparum malaria, which is nonrelapsing, complete eradication could be effected by single injections of this preparation provided certain qualifications were fulfilled.

An inoculum of Entamoeba histolytica, prepared by regular procedures, that was shown incapable of producing lesions in germfree guinea pigs in our previously reported studies gave the same results in the present investigations. However, an inoculum of the ameba cultivated and harvested by modified procedures, which reduced handling and exposure to oxygen and seemed to enhance the vigor of the ameba, produced amebic lesions in the germfree guinea pig. Most of the lesions appeared to originate at the site of the puncture wound through the cecal wall. When the inoculum was introduced without trauma to the cecal wall the number of cecal lesions was significantly reduced. E. histolytica scraped from amebic lesions in germfree guinea pigs and introduced into other germfree guinea pigs produced lesions in a greater percentage of animals than in vitro grown amebas. The amebic infections in germfree animals were purely tissue infections with no evidence of propagation of the ameba in the lumen of the germfree intestine. Fatal amebic enteritis occurred frequently in conventional guinea pigs inoculated as controls for the germfree experiments. There were no fatalities from a similar cause among inoculated germfree animals observed for the same post-inoculation periods.

The long-term use of iodochlorhydroxyquin, 250 mg, 3 times daily, has been employed in 4,000 institutionalized patients over a period of 4 years. Successful prophylaxis against shigellosis and amebiasis was uniformly observed. Successful therapeusis with the same agent against these organisms appears confirmed. Toxic manifestations of such therapy have been extremely infrequent, mild in nature, and completely reversible upon withdrawal of the agent.

A cestode, identified as Bertiella studeri, was obtained after therapy from a 5-year-old boy at Mankato, Minnesota. This case is apparently the first autochthonous infection of man by an anoplocephaline cestode reported in North America. The specimen is described and compared with specimens of B. studeri from a Rhesus monkey in Hamburg, Germany and a cotype of B. mucronata from the Helminthological Collection of the U.S. National Museum. Specificity in the genus Bertiella is discussed.

In hookworm disease parasitic attachment of the adult worms to the intestinal wall appears to be associated with intense eosinophilic reactions locally in the mucosa and even in the submucosa. Concentrated eosinophilic assemblage in the submucosa may indicate deep penetration by the worm. Hemosiderin pigments seen in the biopsy material could represent either hemorrhagic residue or reabsorption of iron lost into the intestine.

Thiabendazole administered to 61 patients with intestinal helminthiasis in single doses of 1.25 or 2.5 grams was found to be effective in Ascaris lumbricoides infection in a dose of 1.25 g. Its action against Ancylostoma duodenale was comparable in effectiveness to 2 g of bephenium or 3 ml of tetrachlorethylene, on the basis of mean percentage reduction in egg-count. It had no marked effect on Trichuris trichiura infection. In a dose of 2.5 g it produced giddiness and vomiting.

Microbiological findings in 276 children under 6 years of age from two isolated communities in Puerto Rico are presented. Enteropathogenic bacteria, namely, enteropathogenic Escherichia coli, Shigella and coagulase-positive staphylococci, were recovered from 31% and 19% of the cases studied at Manzanilla and Cialitos, respectively. Viral agents were recovered from 2.1% of the Cialitos children. A serologic response against cytopathogenic agents was obtained in three-fourths of these cases. Serum survey studies showed previous exposure to certain enteroviruses.

Helminthic and protozoan infection rates were high in both communities. However, most infections were mild. The helminth egg-loads were below those obtained in acute and chronic diarrheas.

The high rate of infection found among nondiarrheic children indicates the importance of existing foci of infection within a population from which infectious agents may be transmitted to susceptibles.

Thirteen chronic stool carriers of Salmonella typhosa were studied to determine the number of typhoid bacilli in stool, gastric juice, and duodenal aspirate before and after intravenous injection of Pancreozymin®. The number of salmonella excreted ranged from 106 to 1010 per gram of feces in 42 of 46 specimens from the 13 patients, and only 1 sample was negative for S. typhosa. S. typhosa was recovered from the pre-pancreozymin duodenal aspirates of only 6 of the 13 patients. However, after administration of pancreozymin, S. typhosa in titers of 104 to 108 per ml was recovered from the duodenal aspirate of every patient. In 12 of the 13 patients the number of salmonella in the post-pancreozymin specimen exceeded by at least 10-fold the number in the pre-pancreozymin specimen.

The present studies show that chronic typhoid carriers regularly excrete large numbers of S. typhosa in stool. The evidence strongly suggests that the biliary tract is the primary site of multiplication in those patients.

Histochemical studies on kidney and liver sections from guinea pigs experimentally infected with Leptospira icterohemorrhagiae (LT-351) demonstrated a pronounced decrease in enzymatic activity for succinic, isocitric, glutamic, and glucose-6-phosphate dehydrogenases and, to a lesser extent, for lactic and malic dehydrogenases. These changes first appeared as patchy areas of diminished enzymatic activity in tissues from animals killed on the fifth day of infection and became widespread in tissues of sixth-day animals. The patchy distribution of lesions and the involvement of mitochondria strongly suggest a hypoxic mechanism as the cause of renal lesions in leptospirosis. Histochemical lesions were less apparent in liver sections than in kidney sections, although a marked decrease in activity was also observed especially for succinic and isocitric dehydrogenases. Biochemical assays of serum and kidney and liver homogenates, on the other hand, did not show variations from those observed in normal animals, although a decrease in activity was noted for isocitric dehydrogenase in sixth-day animals. The decrease in isocitric dehydrogenase is probably due to the decrease in number of mitochondria.

Serum determinations of the various oxidative enzymes and of glutamic-oxaloacetic and glutamic-pyruvic transaminases gave values which were within the normal range of variation and which correlate well with the scarcity of necrotic lesions observed on histologic examination. It is suggested that determination of these enzymes in patients with jaundice will afford valuable information in the differential diagnosis of leptospiral vs. viral hepatitis.

A total of 1,633 skin tests with histoplasmin, performed from 1961–63 on school children in the city of Cali, Colombia and in the nearby rural village of Candelaria, indicated that Histoplasma capsulatum is endemic in Candelaria, whereas in Cali a much lower percentage of positive reactors was found. Some of the possible reasons for the difference are discussed.

Two isolations of St. Louis encephalitis virus are reported from arthropods collected in Pará, Brazil. The first isolate, AR 23379, was obtained from a pool of 35 Sabethes belisarioi; the second, AR 24599, from a pool of 12 Gigantolaelaps sp. combed from Oryzomys macconnelli.

In summary, over the past 9.5 years, there have been 19 isolations of St. Louis encephalitis virus in Trinidad. These have been spread out as follows: 1955, three isolations; 1956, one; 1958, seven; 1960, seven; and 1962, one. One virus strain came from a human being, five came from five species of birds, and 13 came from nine species of mosquitoes.

A strain of St. Louis encephalitis virus was isolated from Culex nigripalpus in Jamaica. It is the first isolation of St. Louis virus on that island.

The presence of St. Louis encephalitis (SLE) virus in Panama first became known in July 1957, when an agent identified at Gorgas Memorial Laboratory (GML) and confirmed by the New York Laboratories of the Rockefeller Foundation as St. Louis encephalitis virus was isolated from a pool of Sabethes chloropterus mosquitoes. These insects were collected in the canopy of the forest in the area of Buena Vista, a few miles east of the Panama Canal, along the Transisthmian Highway.

From July 1957 through July 1959, eight additional isolates of the same virus were made at GML; four of these were from Sabethes chloropterus, two from human serum, and one each from Sabethes spp., Trichoprosopon spp. and Wyeomyia spp. The two isolates from humans were from GML field workers.

Neutralization tests with 195 human sera collected in the area of Paya, Darien in early 1959 revealed that 69 of the sera neutralized one log or more of SLE virus; 27 neutralized 1.5 logs or more; and 16, or 8.4%, neutralized 2 or more logs.

A total of 25,240 mosquitoes was captured in the Tampa Bay area during September and October 1962, using miniature, battery-operated light traps. These were tested in suckling mice in 1,114 pools. A total of 19 isolations of St. Louis encephalitis virus was made, 18 from Culex nigripalpus and a single one from Anopheles crucians. Twenty-nine other virus isolations were made. Twenty-eight were from An. crucians and have been identified as a new virus related to Cache Valley virus of the Bunyamwera arbovirus group; the other was an unidentified virus of the California arbovirus group from Aedes atlanticustormentor.

St. Louis encephalitis virus was isolated on 23 occasions from mosquitoes collected between September 7 and October 25 at widely separated localities of the four-county Tampa Bay area during the St. Louis encephalitis epidemic of 1962. Twenty-two of these isolations were obtained from 485 pools of Culex nigripalpus; the 23rd was from 91 pools of Melanoconion, a subgenus of Culex. The mosquitoes were collected alive in battery-powered light traps and traps baited with ducklings or chicks. These isolations indicate that infected vectors were prevalent over a vast area exposing the human population to infection throughout the region.

Experimental St. Louis encephalitis (SLE) virus infection and transmission studies with Culex nigripalpus revealed that all became infected and nearly 100 percent transmitted. These findings, together with the virus isolations from field-collected individuals in an epidemic area, establish this species as a proven vector of SLE. It was found to be relatively refractory to infection with eastern and western encephalitis viruses.

Two isolations of St. Louis encephalitis virus were made from homing pigeons in central Florida. One of the isolates was obtained from the brain of a dead pigeon and the second from the blood of an apparently healthy one. Twelve of 32 pigeons in the domestic flock from which the isolates were obtained died.