The American Journal of Tropical Medicine and Hygiene - Volume 20, Issue 3, May 1971

Members and guests of The American Society of Tropical Medicine and Hygiene: As Chairman of the Committee, which included Dr. Calvin W. Schwabe and Dr. Robert H. Kokernot, to select a speaker for the 35th annual Charles Franklin Craig Lecture for 1970, I have the honor of introducing Dr. N. Ansari, Chief, Parasitic Diseases, in the Division of Communicable Diseases of the World Health Organization, Geneva, Switzerland. Few men have contributed so much to progress in tropical medicine and parasitology as Dr. Ansari. One can point to concrete achievements in the control of parasitic diseases, and, probably more importantly, to his influence on the large number of professional and government people with whom he has dealt over the years.

Born in Isfahan, Iran, Dr. Ansari comes from a family that can trace its origin back to the 6th century. I remember Dr. Ansari telling me that most of the family

Mr. President, Dr. Kagan, members of the Society, and guests: I must begin by recognizing the signal honour conferred on me and on the organization to which I belong by your invitation to present the annual Craig Lecture. To say that I am most appreciative is a gross understatement.

It was clear that if I accepted, my subject had to concern the parasitic diseases. The many problems relative to malaria had been covered in this lecture several years ago by Clay Huff, in his usual admirable fashion, leaving me free to consider those parasitic diseases that are the direct responsibility of my section of the World Health Organization. With additional reflection came the realization that this platform would provide a unique opportunity to examine a major concern of ours, as well as one approach to its solution, before a most knowledgeable forum. Thus, let me begin with the warning that I am here to seek your responses and to solicit your assistance.

Three forms of immunosuppression (splenectomy, antilymphocyte serum [ALS], and hydrocortisone) were studied in mice infected intraperitoneally with Plasmodium berghei yoelii (2 × 106 parasitized erythrocytes). Splenectomy, performed 10 days before infection, impaired antibody synthesis and converted this self-limited infection to a 100% lethal infection. Antibody was measured by the indirect fluorescent-antibody (IFA) test. ALS (0.3 ml intraperitoneally every 3 days starting 6 days before infection and continuing through the infection) and hydrocortisone (4 mg intraperitoneally daily starting 1 day before infection and continuing through the infection) also impaired both antibody synthesis and recovery, but most mice eventually overcame the infection. In survivors, the appearance of antibody coincided with a decrease in parasitemia, suggesting that a humoral immunity is one of the factors essential to recovery from this malaria.

Three precipitating serum soluble antigens (SAg 1, SAg 2, SAg 3) were demonstrated in the serum of chickens that had been injected with Plasmodium gallinaceum 72 to 80 hours previously. These antigens were detected when the chickens were tested by double diffusion in gel against an antiserum obtained from chickens that survived the infection. The three antigens showed a molecular weight relationship of SAg 1 > SAg 2 > SAg 3 based on their diffusion in gel and elution from Sephadex G-200. They were selectively precipitated by specified concentrations of sodium sulfate and were partially resolved from DEAE-cellulose by increasing molar concentrations of phosphate buffer. SAg 1 was antigenically unrelated to SAg 2 and SAg 3. SAg 2 appeared to contain lipid, as it was precipitated by dextran sulfate.

From 1965 to 1968 in Vietnam, there was a dramatic increase in the proportion of malaria infections caused by Plasmodium vivax. We studied 30 patients with acute vivax malaria in Vietnam and 12 at Walter Reed General Hospital to assess the responsiveness of their infections to suppressive amounts of chloroquine with primaquine (C-P). Each patient was treated with a single C-P tablet containing chloroquine (base) 300 mg and primaquine (base) 45 mg. Clinical and parasitological responses were prompt in all patients. No urine-chloroquine tests performed upon the patients on admission to the hospital in Vietnam showed detectable chloroquine excretion owing to previous drug administration. Failure to take the prescribed C-P chemoprophylaxis probably accounts for the high proportion of vivax malaria in Vietnam.

To provide information on the frequency and distribution of human trypanosomiasis in the Republic of Panamá, we carried out a survey of the rural population in the nine provinces and the San Blas Territory. After direct examination of blood and hemoculture procedures, we examined 12,975 blood samples, corresponding to 10,570 persons, for trypanosomes from January 1965 through December 1969. Trypanosoma cruzi and Trypanosoma rangeli were more prevalent in the rural areas of Central Panamá, including the provinces of Panamá, Colón, and Coclé. Infections with T. rangeli were also recorded in Darién and Bocas del Toro Provinces. Parasitemia was not detected in blood samples examined from Herrera, Los Santos, Veraguas, and Chiriquí Provinces. The samples from the San Blas Territory were also negative. In Central Panamá, both T. cruzi and T. rangeli occur in the same localities. In 16 communities studied in Panamá Province, the infection rate varied from 0.5% to 8.8%. T. rangeli was six times more prevalent than T. cruzi. The annual variation in the prevalence of infections during the 5 years of this study was determined for the villages of Mendoza. Altos del Jobo, and Cerro Cama. Of 160 persons found positive for trypanosomes, 75% were less than 16 years old. Trypanosomes were more frequently detected in children 6 to 10 years old.

Two species of filth-flies, Musca domestica and Chrysomya megacephala, were evaluated for their abilities to acquire and transmit the oocyst of Toxoplasma gondii from the feces of experimentally infected cats. M. domestica contaminated milk with viable Toxoplasma oocysts for about 24 hours after last contact with infectious cat feces and C. megacephala for as long as 48 hours afterwards. Toxoplasma was isolated from larvae and pupae reared in infectious cat feces, but not from newly emerged adult flies.

Serological response to amebic disease was investigated in Africans in Durban. Immunodiffusion (ID), indirect hemagglutination (IHA), and complement-fixation (C-F) tests were done to compare sensitivity of the tests and their value in differentiating between antibodies in an acute infection and those persisting after treatment. Sera were obtained from persons with amebic disease before and at varying times after treatment and from asymptomatic cyst passers and uninfected persons. In invasive amebiasis, the immunodiffusion and indirect hemagglutination tests were similar in their ability to detect antibodies yielding positive results in 95% and 94%, respectively, of the patients studied. The C-F test was the least sensitive of the three methods, with only 65% of patients with invasive amebiasis being positive. In the cyst-passer group, 55.5% and 39%, respectively, were positive by the IHA and ID tests. A high percentage of uninfected persons were positive by both tests; a possible explanation is the persistence of antibodies for more than 3 years after termination of an infection. All three techniques demonstrate the relative stability of antibody levels over a long period.

Microimmunoelectrophoretic analysis (MIEP) was carried out with axenically cultivated Entamoeba histolytica and sera from cases of proved amebic disease. The serum samples were taken before and at varying time intervals after treatment. The antibody response, as determined by immunoelectrophoresis, was related to indirect hemagglutination (IHA) titer and time after successful treatment. Certain antigen-antibody arcs were lost with the passage of time, and the lability and stability of the antibodies or antigens, or both, in human disease is discussed. The value of combining MIEP with IHA for differentiating between antibodies present during active disease and those persisting after cure is also discussed.

Previous studies have affirmed and denied the importance of obstructive vascular lesions in the pathogenesis of portal hypertension in hepatosplenic schistosomiasis. In addition, the relation between anatomic and hemodynamic alterations has not been adequately explained. In this study, vinylite casts of intrahepatic vessels of cadavers with hepatosplenic schistosomiasis were made and compared with those of cadavers with normal livers and with cirrhosis of the liver. Extensive distortion and obstruction of small portal branches was noted with hepatosplenic schistosomiasis mansoni. These lesions were especially marked in the periphery of the liver, and histological sections from the periphery frequently showed portal tracts in which the portal vein branches were occluded or apparently absent. The rich network of anastamosing venules in the portal spaces was apparently derived from the peribiliary venous plexus. An increase in number and size of intrahepatic arterial branches was marked in cases of hepatosplenic schistosomiasis. Increased arterial supply explains the observed maintenance of normal hepatic blood flow in many patients with this disease. Although the cause of portal hypertension is evident, the pathogenesis of Symmers' clay-pipestem fibrosis of the liver is not. The nearly constant association of Symmers' fibrosis and portal hypertension in schistosomiasis indicates a common, or interrelated, pathogenesis for the obstructive lesions and Symmers' fibrosis.

Paromomycin sulfate (Humatin) was used to treat cestode infections in 28 patients. Eight patients with Taenia saginata, 3 with Taenia solium, and four with Diphyllobothrium latum infections were each successfully treated with a single 4-g dose administered over a 1-hour period for adults and a single dose of 75 mg per kg of body weight for children. Twelve of 13 patients with Hymenolepis nana infections were cured. 10 by the single 4-g dose, and 2 of 3 by the administration of 45 mg per kg of body weight over a period of 5 days. The apparent resistance of H. nana to the single-dose regimen is believed to be related to the low absorption of the antibiotic and the inaccessibility of the cysticercoids that are buried deep within the mucosa of the villi.

The larvicidal effect of Dichlorvos® was evaluated against the free-living stages of Ancylostoma caninum in Harada-Mori and charcoal cultures containing Dichlorvos resin pellets. The effect of single pellets on the larvae in water was tested also by transferring pellets periodically, and by exposing larvae for one period and allowing various periods for recovery. Fecal samples from treated dogs were collected until all pellets had been passed and were cultured in charcoal. The drug killed the larvae under all conditions tested. There appeared to be no interference with the development of eggs or the hatching of larvae. However, a few larvae survived to the infective stage (L3). Larvae at all stages of development were equally susceptible to the drug. Posttreatment fecal cultures produced few or no infective larvae. The toxic effects of Dichlorvos appear to be irreversible. The larvicidal properties of the drug may add significance to the benefits of treatment with Dichlorvos in the control of hookworm infection.

A survey of intestinal parasites was done on 846 fecal samples from dogs in a residential area in Chicago. The fecal samples were collected from streets and areas where dogs were walked on leashes. An additional 601 fecal samples collected from dogs and cats brought to area veterinary hospitals were examined for comparison. The prevalence of infections found were 4.25% and 4.33% for ascarids; 3.78% and 4.83% for hookworm; 1.30% and 2.33% for whipworm; 2.71% and 1.33% for strongyloids; 1.65% and 3.83% for other infections. In each of these infections the results in percentages are given first for the street survey and second for the hospital survey.

At the age of 4 months, a boy in Isfahan, Iran, was examined because of an illness, of several weeks, characterized by irritability, cough, diarrhea, sweating, and pallor. After each exacerbation of his illness, he had expelled four worms, which proved to be Moniliformis moniliformis. During the next 5 months, five M. moniliformis were expelled; all were male worms. Repeated stool examinations revealed no helminths or helminth eggs, but Giardia lamblia was found on one occasion. The child had moderate anemia and leukocytosis, with 4% eosinophils. Fourteen days after treatment with thiabendazole, the ninth worm was expelled, and on the 15th day eggs of M. moniliformis were found in a stool specimen. A rat captured in the patient's home was infected with a female M. moniliformis containing eggs. Cockroaches and a lizard caught in the home were not infected with this or other parasites. We believe that a grain beetle in barley, eaten by the child, may have been the intermediate host.

Rhinophycomycosis entomophthorae, a chronic infection of the upper respiratory tract caused by a phycomycete, Entomophthora coronata, is a relatively new disease compared with infections by other fungi of the same class, but different genera, that involve other parts of the body as well. Sixteen cases have been seen, studied, and followed since the disease was first recognized in this unit and reported under the name rhinophycomycosis. Observations suggest that the disease, unlike some other mycotic infections, does not regress spontaneously and that it is not opportunistic. The mode of action of potassium iodide in the treatment of these cases is uncertain, but the drug has proved efficacious from the outset in all but two cases; in these resistance to the drug is thought to have developed through interruption of treatment. Other forms of treatment have been tried, and one of these (sulphamethoxazole with trimethoprim) proved successful in both resistant cases almost simultaneously. Experience suggests that the addition of a sulphonamide is helpful, if not essential, and that surgery should be restricted to biopsies only.

The name “Tuleniy” is proposed for a Group B arbovirus isolated from Ixodes putus ticks collected from rifts in rocks at a seabird colony (Common Murre, Uria aalge inornata) on Tuleniy Island, Sea of Okhotsk. Strain LEIV-6C was shown to be a RNA-containing virus less than 50 nm in size, sensitive to ether and sodium deoxycholate, and pathogenic for infant and 3-week-old mice after intracerebral inoculation. Cross reactivity was demonstrated with several Group B arboviruses by tests using a goose-cell hemagglutinin and a complement-fixing antigen prepared from the agent and hyperimmune serum prepared in rabbits. However, in neutralization tests, the virus was not neutralized by antisera to tick-borne encephalitis, West Nile, St. Louis, and Japanese B encephalitis, nor were these viruses neutralized by antisera to LEIV-6C. Replication of the virus was demonstrated in experimentally infected Aedes aegypti, with biological transmission to suckling mice, and in the tick Hyalomma asiaticum. Three additional strains of virus, recovered from both male and female ticks at the same time and collecting place, were shown to be identical with LEIV-6C.

A Group B arbovirus was isolated from the hard tick Ixodes uriae collected in association with sea bird nesting sites on Three Arch Rocks National Wildlife Refuge, Oregon. The virus killed suckling and 9-day-old mice by both the intracranial and intraperitoneal routes, but killed adult mice only by the intracranial route. It did not kill newly hatched chicks by either route. The virus did not produce plaques in three mammalian cell lines. It did cause cytopathic effects in pig kidney (PK-H13) cells but not in African green monkey-kidney (Vero) or baby hamster-kidney (BHK-21) cells, in four established insect-cell lines, or in primary tissue and cell cultures. Although virus did not grow in four insect-cell or in tick-hemocyte cultures, it did produce persistent, inapparent infection of primary cultures of tick viscera, supporting the premise that it is a true tick-borne virus rather than an errant mosquito-borne one. The virus is sensitive to sodium deoxycholate and ethyl ether, and its size appears to be between 50 and 100 mµ. Serologic tests demonstrated that it is related to several other viruses in Casals' serological Group B. Recent mouse neutralization tests reveal no essential differences between this virus and Tuleniy virus. The occurrence of this virus in both Asia and the United States is of considerable zoogeographic interest.

After the widespread 1967–68 epizoodemic of Venezuelan equine encephalomyelitis (VEE) in areas of low and moderate seasonal rainfall in Colombia, a strain of VEE virus was sought in the high-rainfall region of the Pacific lowlands where previous serological studies had shown past activity of VEE virus in man without indication of overt clinical illness in epidemic form. A total of 20 sentinel hamsters, in two groups, were exposed for 2-week periods, one in July and one in August and September 1969, along the margins of a grass-overgrown, freshwater swampy area 50 km inland from the port of Tumaco near the Ecuadorian border. One hamster yielded VEE virus and two others yielded Eastern equine encephalomyelitis (EEE) virus. Virus was not isolated from 7,199 mosquitoes captured in the vicinity of the exposed hamsters. This isolation of VEE virus confirms the suspected presence of the agent in the Pacific lowlands of Colombia and also the utility of sentinel hamsters for detecting endemic VEE virus activity in the American Tropics. The isolations of EEE virus are the first from Colombia, the first from the west coast of South America, and the first from sentinel hamsters.

On a farm in southwestern Wisconsin, where a case of California encephalitis had occurred, an 18-month study was made of small, forest-dwelling mammals and the appearance of antibodies to California group virus in them. The population densities of the mammals and their movements were obtained from trapping records and the observation of marked animals in the field. Antibodies to CEV, probably LaCrosse virus, developed in 7 of 44 tree squirrels (Sciurus niger and Sciurus carolinensis) between mid-July and mid-December. Highest antibody rates were found in chipmunks, Tamias striatus (53%), and tree squirrels (39%), which by their habits are closely associated with the mosquito Aedes triseriatus. Lower antibody rates were found in cottontail rabbits, Sylvilagus floridanus (15%), flying squirrels. Glaucomys volans (5%), and white-footed mice, Peromyscus leucopus (0%), which have less ecological overlap with A. triseriatus, from which most isolates of LaCrosse virus have been made. We concluded that our findings were consistent with the hypothesis that A. triseriatus is a common vector of CEV among these mammals in southwestern Wisconsin.

Nineteen strains of Sicilian-type and two strains of Naples-type phlebotomus fever virus were recovered from wild-caught Phlebotomus papatasi collected in Cairo. Egypt. Maximum virus transmission appears to occur in August and September, with some activity extending to November. In a comparison of source materials for virus isolation, nonengorged specimens were superior to those containing blood. Suckling mice were a suitable host for primary isolation of both virus types; blind passages and lengthy courses of adaptation to this host were not required. The recovery of Sicilian-type virus from male sandflies was interpreted as evidence for transovarial passage of the virus.