The American Journal of Tropical Medicine and Hygiene - Volume 32, Issue 4, 1983

Methods are described for the cryopreservation of third-stage larvae of Brugia malayi. Optimum conditions utilized larvae free from the mosquito host frozen at the rate of -1° or -0.8°C per min in medium containing 9% dimethyl sulfoxide and 0.004 M polyvinylpyrrolidone. Nonfrozen or thawed larvae were inoculated intraperitoneally into jirds (Meriones unguiculatus), the thawed larvae after cryogenic storage for 5–378 days. In general, the percentage of adult worms recovered at necropsy were comparable between the two groups and ranged from a mean of 6–9% of the larval inoculum. In addition, three of four patas monkeys (Erythrocebus patas) inoculated with thawed B. malayi larvae developed patent infections. The cryopreservation of third-stage larvae of Dipetalonema viteae also is discussed.

An outbreak of trichinellosis occurred in a Chinese family after the ingestion of inadequately cooked pork. Diagnosis was established by the demonstration of antibodies against Trichinella spiralis larval antigen by crossed immunoelectrophoresis and enzymelinked immunosorbent assays, and living larvae in muscle biopsy. The main presenting symptom of these patients was pyrexia. Typical clinical features of Trichinella infection such as periorbital edema and severe myalgia were either minimal or absent. A history of having eaten insufficiently cooked meat is thus extremely important for correct diagnosis. We believe that this is the first documented report of a Trichinella outbreak in Chinese living in Hong Kong.

Phenol sulfuric test active peak (PSAP), a schistosome-specific antigen was radiolabeled with Bolton-Hunter reagent, purified, and used in two radioimmunoassays which measured total and IgG-specific antibodies in acutely, early, and chronically Schistosoma mansoni-infected patients. Molecular sieving and lectin chromatography were used to purify PSAP. In Sepharose 4B chromatography PSAP was the only antigenic substance and was one of four distinct peaks. PSAP adhered to concanavalin A and was purified after elution with α-methylmannoside. Total antibody to purified radiolabeled PSAP was measured using polyethylene glycol to precipitate complexes formed after the addition of label to varying dilutions of sera, while Staph A was used to precipitate IgG containing complexes. Most non-IgG-specific antibody was IgM. Since antibody responses were dependent on intensity of infection, ratios of the percent Staph A precipitation to the percent polyethylene glycol precipitation were determined in patients with known duration of infection. Patients with acute schistosomiasis showed depressed ratios indicative of high IgM antibody and low IgG levels, while chronically infected patients had elevated ratios. Thirty-nine sera from acutely or chronically infected patients were evaluated blindly. Twenty-four of 27 patients with clinically diagnosed acute schistosomiasis had detectable antibodies to PSAP and these were correctly classified as acutely infected. Five of six chronically infected patients had anti-PSAP responses and all were correctly identified. Levels of antibodies to a gut-associated proteoglycan, another specific schistosome antigen, enabled correct classification of all but one of the remaining patients. Serologic responses to specific parasite antigens can differentiate acutely infected patients from those chronically infected.

A study was performed to determine the extent of attrition of Schistosoma mansoni in naive mice (innate resistance) during the 1st week of infection. Each mouse was exposed to exactly 50 cercariae radiolabeled with [75Se] selenomethionine. On 1, 4, and 7 days postexposure, skin, lungs and liver were analyzed by compressed organ autoradiography for the presence of labeled larvae. Using this technique it was determined that no more than one-third of the 59% attribution that occurred between the cercarial and adult worm stages could be attributed to losses during the skin phase; most of the attrition in naive mice occurred after the migration of larvae to the lungs.

Mice immunized by percutaneous exposure to ultraviolet-irradiated Schistosoma mansoni cercariae developed levels of resistance to subsequent S. mansoni infection comparable to those induced by gamma-irradiated cercariae (50–70% reduction in adult worm burden). Cercariae treated with ultraviolet doses ranging from one to three times the minimum dose required to prevent long-term survival induced the highest levels of resistance.

Four cases of phaeohyphomycosis in the form of chronic and isolated cysts are presented. The cysts were strictly confined to the subcutaneous tissue, with no involvement of the corresponding skin. Patients were asymptomatic, without satellite lesions or regional lymphadenopathy. The clinicopathologic importance of this type of phaeohyphomycosis is discussed. As far as we know, our cases are the first described from Brazil.

We identified Exophiala spinifera as the causal agent in a case of subcutaneous phaeohyphomycosis in El Salvador. Identification was based on the morphology of the fungus in tissue and the microscopic features of the culture obtained from the biopsy material. This case is the first of this type to be documented from Central America.

Oral rehydration solutions (ORS) containing 90 mmol/liter or 50 mmol/liter of sodium have been successfully used in the treatment of hospitalized well-nourished and undernourished children; however, few data are available on the use of these ORS in well-nourished ambulatory children with minimal dehydration. We therefore compared the safety and efficacy of both ORS with standard outpatient management in a controlled, randomized study among 93 well-nourished children aged 3 months to 2 years, with minimal dehydration secondary to acute diarrhea at an outpatient clinic in Panama. Patients in all three groups were hydrated successfully. However, patients in both ORS groups gained significantly (P < 0.05) more weight at the 2-week follow-up compared to the control group. There were no complications due to the use of either ORS. No child developed hypernatremia nor hyponatremia during therapy. These studies indicate that both ORS (containing 90 or 50 mmol/liter of sodium) are effective and safe in hydrating well-nourished ambulatory children with minimal dehydration.

Ten cases of pyomyositis of the iliacus muscle are described in otherwise healthy young Samoans. The correct diagnosis was frequently delayed. Staphylococcus aureus was the most common pathogen isolated from drained abscesses. Preference for hip flexion was seen in six patients, and localized pain or induration at the anterior superior iliac spine were found in seven patients. These clues may help expedite a correct diagnosis.

In 1973, 1978, and 1981, cases of cholera were acquired along the Gulf Coast of the United States. The isolates from all of the cases were toxigenic Vibrio cholerae O-group 1, biotype El Tor, serotype Inaba, hemolytic, and of the same phage sensitivity pattern, and all had the same restriction endonuclease pattern by molecular genetic analysis. The strain from one of the two 1981 cases differed from the others in having a small plasmid and a negative Voges-Proskauer reaction. Multiple importations, chronic carriers, and continuous occurrence of undetected cases are unlikely explanations for these findings, which suggest that toxigenic V. cholerae 01 can multiply and persist for years in some environments, making eradication of cholera a formidable task.

Spirochetes were observed in the midguts of 35% of 147 motile Ixodes dammini from three locations in Lyme and East Haddam, Connecticut. Positive ticks were removed from eastern chipmunks (Tamias striatus), raccoons (Procyon lotor), white-footed mice (Peromyscus leucopus), and a red squirrel (Tamiasciurus hudsonicus). Spirochetes were isolated in fortified Kelly's medium from nine questing or partially engorged I. dammini adults and nymphs and from the bloods of a raccoon and a white-footed mouse. Connecticut isolates from ticks and mammals were serologically indistinguishable from the original Shelter Island, New York strain when cross-tested by immunofluorescence against their mouse antisera. Sera from eight patients diagnosed as having Lyme disease contained antibodies to spirochetes isolated from ticks and mammals. Our finding of serologically and morphologically indistinguishable spirochetes in a raccoon, white-footed mouse and ticks suggests that closely related serotypes are present in wild mammals commonly parasitized by I. dammini, and further supports the claim that a spirochte is involved in the etiology of Lyme disease.

In order to determine the degree of mucosal infectivity of the attenuated XJCl3 strain of Junin virus, guinea pigs were orally or nasally inoculated. Infectivity was 85% for the oral and 100% for the nasal route, as detected by death or serum antibody development. The presence of serum antibodies was closely associated with resistance to challenge with the XJ pathogenic strain, which killed 100% of controls when inoculated by the parenteral or nasal route. However, mortality rates after mucosal infection were low, depending on the dose. Guinea pigs which survived nasal inoculation developed serum neutralizing antibodies, and were fully resistant to challenge with the XJ pathogenic strain.

Lassa virus infection and antibodies were studied in households where Lassa fever cases occurred, and compared to those in nearest neighbor houses and “far” houses located across the village from case houses. Seventy-nine percent of all rodents caught in the houses were Mastomys, the natural reservoir of Lassa virus. Rodent infection was not randomly distributed, but rather focal. Thirty-nine percent of the Mastomys in case houses were viremic, compared to 3.7% in control houses. Human antibody prevalence in case houses was 30%, compared to 20% in non-case houses (P < 0.05, chi-square test, df = 2). Neither seroconversions nor antibody prevalence rates were associated with household size or number of persons per room. Trapping of rodents in half of the case and control houses resulted in a Mastomys reduction ranging from 2.2- to 3.3-fold. This reduction failed to significantly reduce the seroconversion rate to Lassa virus in the people of trapped houses compared to those in untrapped ones. More complete trapping will be needed in order to better evaluate this procedure as a means of interruption of Lassa virus transmission in endemic villages.

La Crosse (LAC) virus (California encephalitis serogroup) was identified as the etiologic agent of disease in 61 cases of California encephalitis (CE) that occurred in Illinois between 1976 and 1980. This group represented 54% of all 114 laboratory-diagnosed cases of CE between 1966 and 1980. Key epidemiologic observations included: 88% of the 61 cases had onset in July, August, or September; the 5- to 9-year-old age group represented 48% of the cases; the male: female sex ratio was 2:1; 97% of the cases occurred in the northern half of the state; and 61% of the cases occurred in Peoria County. Four instances of probable common source of exposure were reported. Average length of hospitalization was 8.3 days (range 3–31 days). Hospitalization costs were estimated at $3,967–$5,750 per case. An “average” year in Illinois yields 12 cases of LAC encephalitis with direct hospitalization costs of $47,604–$69,000.

Experimental infection of 11 Bradypus variegatus and Choloepus hoffmanni sloths with St. Louis encephalitis (SLE) virus produced detectable viremias of seven to 27 (median 13) days duration and maximum titers of 2.7 to 6.5 (median 5.1) log10 median suckling mouse intracranial lethal doses (SMicLD50) per ml. Experimental SLE viremia onset was delayed and maximum titer depressed in two sloths concurrently infected with naturally acquired viruses. SLE viremias in four experimentally inoculated cormorants Phalacrocorax olivaceus were shoter, and of equal or lower titer, than in sloths. Colonized Culex pipiens quinquefasciatus mosquitoes were infected by feeding on sloths circulating at least 4.8 log10 SMicLD50 of SLE virus per ml, and subsequently transmitted the infection to mice and chicks. An uninoculated baby Bradypus became infected by contact transmission from its mother. The antibody response of sloths to SLE virus was slow, being undetectable until several weeks post-inoculation. However, both sloth species developed high and long-lasting neutralizing and hemagglutination-inhibition antibody titers. The complement-fixation antibody response in Bradypus was lower and slower to develop than in Choloepus. Sloths with naturally acquired SLE virus antibody did not become detectably viremic after experimental inoculation. Neither sloths nor cormorants become overtly ill from SLE virus infection.

Plasmas of sloths and other Central Panamanian wild vertebrates were tested for plaque-reduction neutralizing (PRN) antibodies against four flaviviruses and one alphavirus. Forty percent of 97 two-toed sloths, Choloepus hoffmanni, and 8% of 168 three-toed sloths, Bradypus variegatus, were specifically positive against St. Louis encephalitis (SLE) virus. The prevalence of antibody against SLE virus was considerably higher in sloths than in any other group of wild vertebrates tested, including birds, and was found mainly in adult sloths. Specific PRN antibody against yellow fever (YF) virus was found only in monkeys. A high prevalence of PRN antibody against Ilheus and Mayaro viruses was detected in agoutis, Dasyprocta punctata, and against Mayaro virus in howler monkeys, Alouatta villosa. No plasma was specifically positive against Bussuquara virus. The results are interpreted as evidence that sloths are probably not important hosts in jungle VF cycles, but may be significant amplifying hosts in tropical SLE virus cycles.

The growth of Rio Grande (RG) virus, the only phlebovirus known to occur in the United States, was studied in Lutzomyia anthophora, its suspected sand fly vector. RG viral titers in infected flies increased more than 10,000-fold within 7 days after intrathoracic inoculation. Experimentally infected female L. anthophora transmitted virus transovarially (vertically) to 54.8% of their F1 progeny. This is the first virologically confirmed demonstration of transovarial transmission of a phlebovirus by sand flies. It indicates one mechanism by which RG and possibly other phleboviruses may be maintained in nature.

Four serotypes of bluetongue virus (BTV-10, 11, 13 and 17) have been identified in the United States. Analyses of the genome RNA segments and viral induced polypeptides of U.S. prototype BTV-17 virus by comparison with the corresponding macromolecules of earlier isolates of BTV-11 serotype support the hypothesis that BTV-17 originated by genotypic and antigenic drift from a BTV-11 serotype virus.

In 1971, an unusual strain of Venezuelan encephalitis (VE) virus (71D1252) was recovered from the same small area of a rain forest in the western Amazon basin of South America near Iquitos, Loreto, Peru, from which strains of subtype I-D were recovered. The marker characteristics of this strain resembled most closely those of VE subtype III (Mucambo) and were distinctly different from coexisting I-D strains. Thus the concurrent presence of two different VE virus subtypes in one place was a striking exception to the usual geographic allopatry of VE virus subtypes. Strain 71D1252 also contained temperature sensitive (ts) (37°C versus 39°C) virions in the original mosquito suspension and first suckling mouse passage brain tissue suspensions. It thus represents one of the few so-far-reported ts strains of viruses found in nature, and the only natural ts strain of VE virus.

Three hundred seventy-nine virus isolates were obtained from mosquitoes collected and sentinel hamsters exposed in coastal Ecuador from 1974 to 1978. These included four alphaviruses [Venezuelan equine encephalitis 1B (1), Venezuelan equine encephalitis 1D (35), western equine encephalitis (1) and eastern equine encephalitis (4)]; two flaviviruses [St. Louis encephalitis (3) and Naranjal (6)]; 11 bunyaviruses [Maguari (243), Playas (3), Vinces (33), Turlock (2), Abras (5), Babahoyo (3), Acara (2), Guajara (3), San Juan (6), Pueblo Viejo (3), 18 unspecified Gamboa serogroup viruses, Palestina (7)]; and one vesiculovirus (vesicular stomatitis New Jersey). All but Venezuelan equine encephalitis virus were new to Ecuador, and Naranjal (serogroup B), Playas (Bunyamwera serogroup), Vinces (serogroup C), Abras and Babahoyo (Patois serogroup), San Juan and Pueblo Viejo (Gamboa serogroup) and Palestina (Minatitlan serogroup) are newly recognized viruses. These isolates have enabled us to 1) expand our knowledge of the geographic distribution of recognized viruses, 2) expand our knowledge of the members of certain serogroups and 3) establish two new serogroups (Gamboa and Minatitlan).