Tularemia: a 30-year experience with 88 cases.

Drawing upon our experience with 88 cases and a survey of the English literature, we reviewed the clinical, pathophysiological, and epidemiological aspects of tularemia. Tularemia can be thought of as two syndromes--ulceroglandular and typhoidal. This dichotomy simplifies earlier nomenclature and emphasizes the obscure typhoidal presentation. Clinical manifestations suggest that the two syndromes reflect differences in host response. In ulceroglandular tularemia the pathogen appears to be well contained by a vigorous inflammatory reaction. Pneumonia is less common and the patient's prognosis is good. In typhoidal disease there are few localizing signs; pneumonia is more common; and the mortality without therapy is much higher, suggesting that the host response is somehow deficient. Francisella tularensis is an extremely virulent pathogen capable of initiating infection with as few as 10 organisms inoculated subcutaneously. During an incubation period of 3 to 6 days the host responds first with polymorphonuclear leukocytes and then macrophages. Granulocytes are unable to kill the pathogen without opsonizing antibody leaving cellular immunity to play the major role in host defense. One to 2 weeks after infection, a vigorous T-lymphocyte response can be detected in vitro with lymphocyte blast transformation assays and in vivo with an intradermal skin test, which, unfortunately, is not commercially available. Humoral immunity, often used as a diagnostic modality, appears 2 to 3 weeks into the illness. Cellular immunity is long-lasting, accounting for the common reoccurrence of localized disease upon repeated exposures to the pathogen. There are no symptoms that distinguish the ulceroglandular from the typhoidal syndrome. A pulse-temperature dissociation is seen in less than half of the patients. The location of ulcers and enlarged lymph nodes give a clue to the likely vector since lesions located on the upper extremities are more commonly associated with mammalian, and those of the head and neck and lower extremities with arthropod, vectors. Pharyngitis, pericarditis, and pneumonia can complicate both syndromes, although the latter is much more common in typhoidal disease. Hepatitis, usually of a mild degree, is common and occasionally erythema nodosum is seen. No specific laboratory tests characterize tularemia, and cultures of the pathogen are often difficult to obtain because of the special growth requirements of Francisella tularesis and the inability of many clinical laboratories to handle the dangerous pathogen.(ABSTRACT TRUNCATED AT 400 WORDS)

Serologic analyses of Peromyscus leucopus, a rodent reservoir for Borrelia burgdorferi, in northeastern United States.

An enzyme-linked immunosorbent assay (ELISA) and indirect fluorescent-antibody test were used to detect antibodies to Borrelia burgdorferi, the causative agent of Lyme disease, in Peromyscus leucopus (white-footed mouse). Of the 661 mice captured in Connecticut, Rhode Island, and New York during 1980 and 1983 to 1987, 166 (25.1%) had antibodies to B. burgdorferi by ELISA. Comparative analyses of 210 serum specimens, collected in areas where Lyme disease is endemic, revealed a threefold difference in sensitivity between the ELISA (38.1% positive) and the indirect fluorescent-antibody method (12.4%). Although prevalence of seropositive P. leucopus was highest during June, elevated amounts of antibody (1:1,280 to 1:2,560) were detected in mice that harbored spirochetes during all seasons. Being reservoirs for B. burgdorferi, these rodents are suitable for monitoring spirochete infections at foci and should be included in field evaluations of control programs aimed at suppressing Lyme disease.

Aeromonas hydrophila infection associated with the use of medicinal leeches.

The use of medicinal leeches (Hiruda medicinalis) is becoming more common after plastic surgery to control venous congestion of skin grafts. We describe a patient with Aeromonas hydrophila infection whose graft was treated with medicinal leeches. The infection required systemic antibiotic therapy. A. hydrophila is the predominant bacterial flora in the gut of the leech, where it plays an essential role for the animal in the digestion of blood. The potential for A. hydrophila wound infection, and appropriate antibiotic prophylaxis of the leech or patient, should be considered when medicinal leeches are used.

An arenavirus isolated from wild-caught rodents (Pramys species) in the Central African Republic.

We isolated nine arenavirus strains from blood and/or tissues of Praomys sp. rodents wild-caught in derived savannah and forest gallery areas of the Central African Republic (CAR). Convalescent serum from either humans or animals infected by Lassa, Mozambique, or lymphocytic choriomeningitis virus cross-reacted with the strains from the CAR. However, monoclonal antibodies to these three viruses gave a profile against the CAR strains suggesting major antigenic differences between each of them and the CAR virus. These data along with the fact that other African arenaviruses have been recovered from Mastomys natalensis and not Praomys suggest that this virus is significantly different from the others.

[The rodent. Akodon arviculoides, Wagner, 1842 (Cricetidae)--importance in plague foci in Brazil]. / Estudo do roedor Akodon arviculoides, Wagner, 1842 (Cricetidae)--importância nos focos pestosos do Brasil.

The occurrence of the rodent Akodon arviculoides Wagner, 1842 in the plague focus of the "Agreste" region of the State of Pernambuco and a report on its ability for survival, reproduction and development in captivity, its susceptibility to Yersinia pestis infection and the role of this rodent species in Brazilian plague foci are reported.

The herring gull Larus argentatus as a carrier of salmonella.

The proportion of salmonella carriers among town-nesting herring gulls increased significantly from 2.1% in 1975-6 to 8.4% in 1979. The range of serotypes carried by herring gulls was similar to that causing infection in man, and it is likely that the gulls ingest these serotypes when feeding at untreated sewage outfalls on the coast. This is supported by the proportion of salmonella carriers being higher among first-year birds (9.7%) than among older birds (2.0%), as it is known that higher proportions of immature herring gulls feed on the coast. Herring gulls carrying salmonellas appeared healthy at the time of capture and at a later date it was assumed that they were not themselves infected. However, their habit of congregating in large numbers on reservoirs and rubbish tips and also at resting sites on farmland often far from feeding and roosting areas, multiplies the pollution problem and increases the potential health hazard for both man and farm stock. Herring gulls feed at a variety of sites and fly many miles from food source to food source and from feeding areas to the roost. Thus, even within the same day, there is the possibility of the transfer of salmonellas over a much wider area than previously considered.

Parasite-parasite interaction of Salmonella typhimurium and Schistosoma.

The parasite-parasite interaction of Salmonella and Schistosoma was studied. Salmonella typhimurium LT2 was found to associate in vitro with three human species of Schistosoma: Schistosoma mansoni, Schistosoma haematobium, and Schistosoma japonicum. Genetic mutants of S. typhimurium were allowed to interact with ligatured and unligatured worms of S. mansoni in vitro. These studies were undertaken to elucidate the mechanism(s) of the parasite-parasite interaction of Salmonella on the surface of Schistosoma. The ga/E and fla mutants showed 100% association with male schistosomes, but a reduced interaction with female worms. The rough A and pili mutants showed a significant reduction in the ability to associate with both male and female S. mansoni. Observations with the scanning electron microscope revealed that pili function in adhesion of Salmonella to the surface tegument of S. mansoni and S. haematobium. The association of Salmonella and Schistosoma may contribute to persistence of salmonella infection.

Epidemiological studies on the background of the endemic occurrence of tsutsugamushi disease in Toyama Prefecture. I. Epidemiology of infection with Rickettsia tsutsugamuchi among field rodents in endemic and nonendemic areas.

In order to clarify the epidemiological background of the endemic occurrence of tsutsugamushi disease in Toyama Prefecture, Japan, since 1978, comparative surveys have been carried out between endemic and nonendemic areas. Rickettsia tsutsugamushi (Rt) was isolated at a rate of about 36% (158/439) from field rodents in the endemic area while it was not isolated from any of 280 in nonendemic areas. In all of six stations in the endemic area, a significantly high proportion of rodents were found to be Rt carriers. However, no Rt was isolated from rodents captured from July to September. The organism was isolated from rodents captured in the other months, especially in a high proportion in November when infestation of rodents with Leptotrombidium pallidum was at its peak. When the rodents were examined by indirect immunofluorescence staining, the rate of anti-Rt antibody-positive animals was about 55% (157/287) and about 17% (62/368) in endemic and nonendemic areas, respectively. Larvae of mites collected from the rodents were found to belong to four genera and 11 species. Among them L. pallidum was the only mite that had been known to be a vector of Rt. L. pallidum was found most frequently and in abundance from rodents in the endemic area, whereas it was present in very small numbers in rodents in nonendemic areas. The infestation of rodents with L. pallidum showed a seasonal variation, i.e. two peaks per year, in spring and autumn, and the number of mites detected was markedly greater in November than in spring. Rt was isolated from L. pallidum on rodents captured in the endemic area.

Arbovirus vector ecology studies in Mexico during the 1972 Venezuelan equine encephalitis outbreak.

Virus vector studies were conducted in the States of Durango, Chihuahua, and Tamaulipas, Mexico, in June and July 1972. Apparently only a low level of Venzuelan equine encephalitis (VEE) virus transmission to equines occured at the time of the study, and the infection was restricted to areas which had not experienced overt activity during the preceding year. The low level of infection was associated with a scarcity of mosquitoes. The IB (epidemic) strain of VEE virus was isolated from two pools of Anopheles pseudopunctipennis (Theo.) and the blood of one symptomatic equine. The low mosquito population, the relatively few equine cases observed, and the absence of reports of VEE human disease from the outbreak area suggested VEE virus persistence through a low-level mosquito-equine transmission cycle. Other studies have already indicated that wild vertebrates play no more than a minor role in outbreaks of epidemic VEE. Mosquito collections made in areas of the states of Durango, Chihuahua, and Tamaulipas, where considerable epidemic activity of VEE had occurred in 1971, failed to reveal evidence of VEE virus persistence. Twenty-nine ioslations of other arboviruses were also made in these studies: including 22 of St. Louis encephalitis virus (SLE), 2 of Flanders virus, 1 of Turlock virus, 1 of Trivittatus virus of the California Group, 1 of western equine encephalitis virus (VEE), and 2 (from Santa Rose) which possibly represent a hitherto unknown virus in the Bunyamwera Group. These are the first reports of SLE virus isolations from mosquitoes in Mexico, and the first demonstration of Trivittatus, VEE Turlock and Flanders viruses in Mexico from any source.

The herring gull Larus argentatus as a likely transmitting agent of Salmonella montevideo to sheep and cattle.

This paper presents evidence for the involvement of herring gulls (Larus argentatus) as vectors in the recent outbreaks of Salmonella montevideo in sheep and cattle in Scotland and suggests that the transfer can take place over considerable distances. The breeding area in Scotland of herring gulls which overwinter in N.E. England is remarkably similar to the geographical distribution of the outbreaks. This pattern, together with the feeding behaviour of herring gulls on farmland, the presence of S. montevideo in herring gulls just before their departure from the wintering area and the timing of the return just before the peak of outbreaks are all circumstantial evidence implicating this gull in the outbreaks. The rapid return of these gulls to their breeding areas means that S. montevideo can be transported long distances in one day and raises the possibility that the original source of S. montevideo could have been in N.E. England rather than in Scotland.

Epidemic Venezuelan equine encephalitis in North America in 1971: vertebrate field studies.

Epidemic Venezuelan equine encephalitis in North America in 1971: vertebrate field studies. Am J Epidemiol 101:36-50, 1975.-In June 1971, epidemic Venezuelan equine encephalitis (VEE) invaded the lower Rio Grande Valley in south Texas. The Boca Chica area of Cameron County was selected as a study site to investigate vertebrate involvement in the natural cycle of epidemic VEE on the basis of considerable evidence of VEE virus activity there in equines, humans, and mosquito vectors. Only one VEE virus isolation was made from 4739 wild and domestic non-equine vertebrates, although numerous equine and human VEE virus isolations were made in concurrent studies. Serologic studies indicated that VEE virus activity was far greater in large domestic animals than in wild birds, wild mammals, or reptiles. Apparently epidemic VEE virus failed to establish itself in a wild vertebrate cycle in south Texas, since VEE antibody was found only in rabbits in 1972. Eventual cessation of VEE transmission in south Texas has been attributed 1) to the elimination of equines as a source of VEE virus by death, naturally acquired antibodies, or vaccination, 2) to quarantines, 3) to mosquito control, and 4) to the failure of epidemic VEE virus to become established in the wild vertebrate population. Equines emerge as the most important vertebrate host in the amplification and spread of virus during an epidemic of VEE.

Recurrence of Pelecypod-associated cholera in Sardinia.

From Oct. 30 to Nov. 7, 1979, 10 people in the Sardinian province of Cagliari had onset of bacteriologically confirmed cholera. Two symptom-free excretors of Vibrio cholerae O:1 were detected in household contacts of the patients. There were no deaths. All but 1 of the 12 people with V. cholerae O:1 infection gave a history of recent consumption of marine bivalves known locally as arselle (pelecypods). Triplicate matched neighbourhood controls for each of the first 7 cases identified were also interviewed; none had recently eaten arselle. V. cholerae O:1 was also recovered from samples of water and bivalves obtained from a lagoon on the outskirts of the city of Cagliari. Arselle had also been implicated as the vehicle of transmission in 1973 in the last outbreak of cholera in Sardinia. It seems unlikely that cholera transmission had persisted locally in the interim.