Transmission study of Andes hantavirus infection in wild sigmodontine rodents.

Our study was designed to contribute to an understanding of the timing and conditions under which transmission of Andes hantavirus in Oligoryzomys longicaudatus reservoir populations takes place. Mice were caged in test habitats consisting of steel drums containing holding cages, where seronegative rodents were exposed to wild seropositive individuals by freely sharing the same cage or being separated by a wire mesh. Tests were also performed for potential viral transmission to mice from excrement-tainted bedding in the cages. Andes virus transmitted efficiently; from 130 attempts with direct contact, 12.3% resulted in virus transmission. However, if we consider only those rodents that proved to be infectious, from 93 attempts we obtained 16 infected animals (17.2%). Twelve of them resulted from intraspecies O. longicaudatus encounters where male mice were differentially affected and 4 resulted from O. longicaudatus to Abrothrix olivaceus. Experiments using Abrothrix longipilis as receptors were not successful. Transmission was not observed between wire mesh-separated animals, and mice were not infected from excrement-tainted bedding. Bites seemed not to be a requisite for oral transmission. Genomic viral RNA was amplified in two out of three saliva samples from seropositive rodents, but it was not detected in urine samples obtained by vesicle puncture from two other infected rodents. Immunohistochemistry, using antibodies against Andes (AND) hantavirus proteins, revealed strong reactions in the lung and salivary glands, supporting the possibility of oral transmission. Our study suggests that AND hantavirus may be principally transmitted via saliva or saliva aerosols rather than via feces and urine.

Immunization with outer surface protein (Osp) A, but not OspC, provides cross-protection of mice challenged with North American isolates of Borrelia burgdorferi.

The identification of antigens with the capacity to induce a broad spectrum of protective immunity is an important consideration in the design of a Lyme disease vaccine. In this study, the range of protection provided by outer surface protein (Osp) A or OspC vaccination was compared. Mice actively immunized with OspA or OspC were challenged with 3 North American isolates of Borrelia burgdorferi. OspA-immunized mice were fully protected from infection with each of the isolates, whereas mice immunized with OspC were protected from infection with the homologous isolate but not with 2 heterologous isolates. Sequence analysis revealed that the ospA genes from these 3 isolates were >99% homologous, whereas the ospC genes shared only 81%-85% homology. Western blot analysis suggested antigenic heterogeneity associated with OspC but not OspA. These results indicate that genetic and antigenic heterogeneity may limit the usefulness of OspC as a vaccine constituent.

A survey of bovine, bubaline and swine sarcocystosis in the Philippines.

In a survey conducted from January to December, 1994, muscle tissues in 12 out of 22 slaughtered carabaos ages 8-17 years old and obtained from the Food Terminal Inc, Abbatoir in Laguna showed numerous white and creamy elliptic-shaped soft bodied macrocysts in the throat muscles. Microscopic examination of the throat and cardiac muscle tissues revealed the presence of fusiform-shaped microcysts. Our observations are consistent with previous reports incriminating Sarcocystis fusiformis as the most important etiologic agent of bubaline sarcocystosis in the country. In a survey of bovine sarcocystosis in muscle tissues of imported Australian cattle (Brahman Breed) and native cattle obtained from various slaughter houses in Manila and suburbs, prevalence rates of 17% (98/577) and 3% (1/31) were noted, respectively. Sarcocysts were predominant in skeletal muscles and to a lesser extent in cardiac, esophageal and diaphragm muscle tissues. Light microscopic examination of sarcocysts morphology suggests Sarcocystis cruzi (= Sarcocystis bovis), and Sarcocystis hominis (= Sarcocystis bovihominis) or Sarcocystis hirsuta (= Sarcocystis bovifelis) as the likely etiologic agents of bovine sarcocystosis in the country. Of the 225 swines examined, only muscle tissues from a 6-month old swine revealed very young sarcocysts (= metrocytes). A review of available documented studies on sarcocystosis suggests that to date, our findings may represent the first data on the prevalence of bovine and swine sarcocystosis in the Philippines.

Transposition of IST2 in Thiobacillus ferrooxidans.

The genome of Thiobacillus ferrooxidans contains at least two different repetitive DNA elements. One of these elements, termed IST2 has been sequenced and shown to exhibit the characteristics of a typical prokaryotic insertion sequence. Furthermore, preliminary evidence has implicated IST2 in genomic rearrangements, although the mechanism of rearrangement, whether by transposition or recombination, has not been established. In this report we provide evidence from detailed restriction enzyme analyses and DNA sequencing data that support a model of transposition, consistent with the notion that IST2 is a mobile insertion sequence.