Cohorts for the study of HIV­1-exposed but uninfected individuals: benefits and limitations.

Since the late 1980s, with the first identification of individuals who were exposed to human immunodeficiency virus type 1 (HIV-1) yet remained uninfected, or "HIV-1-resistant" individuals, a large number of cohorts that include HIV-exposed seronegative (HESN) subjects have been identified globally for the purpose of investigating the genetic, immunologic, and environmental factors that may help alter susceptibility to HIV-1. In this article, in light of the recent International Symposium on Natural Immunity to HIV, we review the characteristics of different groups with respect to their relative risks and briefly summarize the known cohorts that include exposed uninfected subjects worldwide.

An extended outbreak of congenital chondrodysplasia in calves in South East Australia.

OBJECTIVE: To report an outbreak of congenital chondrodystrophy in calves in South East Australia. METHODS: District veterinarians investigated reported cases of calf deformities. Owners of affected herds were interviewed using a standard questionnaire to identify potential risk factors. Dams of several affected calves were serologically tested for Akabane virus, Aino virus, pestivirus and bluetongue, and affected calves were tested for pestivirus antigen and serum immunoglobulin concentrations. Gross and histopathological examinations of numerous calves were performed, concentrating on the musculoskeletal system. RESULTS: A case definition of distinctive skeletal deformities was established, and 89 property owners reported calves with chondrodystrophy in Spring 2003, 2004 or 2005. Some 14 property owners reported affected calves in more than one year. Prevalence and severity of deformity varied greatly between and within properties. None of breed, sex, age of dam, lineage, pasture type, supplementary feeding, fertiliser use or toxic plants was consistently associated with the disease. All dams experienced hot, dry conditions during the first trimester of pregnancy and were exposed to adverse conditions thereafter. Consistently dams were reported to have been grazing undulating to hilly terrain during early pregnancy. All serological tests were negative for Akabane virus, Aino virus, pestivirus and bluetongue. Histopathology of affected skeletal samples showed chondrodysplasia. CONCLUSION: The outbreak had similarities with previous outbreaks reported in the region. No specific aetiology could be determined. There is some evidence that the cause of the deformities could be a manganese deficiency during foetal development. Ongoing work to test this hypothesis is therefore warranted.

Plasmodium infection in a Leadbeater's possum (Gymnobelideus leadbeateri).

CASE REPORT: A wild-caught, adult female Leadbeater's possum (Gymnobelideus leadbeateri) died while in captivity after suffering from chronic ill-thrift that progressed to acute respiratory distress. On histopathological examination of tissues, the cause of death was determined to be severe acute pneumonia with pulmonary oedema associated with an intracellular protozoan parasite present within erythrocytes. Transmission electron microscopy was performed on lung tissues and organisms consistent for Plasmodium sp. were identified within numerous erythrocytes. Molecular characterisation of the parasite from DNA extracted from tissue blocks of fixed lung determined the organism to belong to the genus Plasmodium (100% similarity to Plasmodium species when a BLAST analysis was performed); however, speciation of the organism was not possible. CONCLUSION: This is the first report of Plasmodium sp. infection and subsequent disease in a native Australian mammal. The lifecycle of this parasite remains unknown. It is also unknown what effects haemoparasitism may have on the population dynamics of this endangered possum species.

Chondrodysplastic calves in Northeast Victoria.

Outbreaks of chondrodysplasia in calves occur sporadically every 10-15 years, particularly following prolonged drought conditions, throughout Northeastern Victoria and the Southern Tablelands of New South Wales, Australia. An outbreak spanning 2 calving seasons (2003-2004) involving numerous losses through stillbirth, perinatal loss, and poor growth was investigated. Investigations of 4 representative cases are presented here with a definition of the gross and histopathologic defects and an overview of epidemiologic data gathered from affected farms. Calves showed variable disproportionate dwarfism without arthrogryposis. Long bones were shortened and showed axial rotation. Articular surfaces were distorted with misshapen weight-bearing surfaces associated with variable thickness of articular cartilage. Physes were distorted and variable in thickness with occasional foci of complete closure. The major histologic abnormality in the physes was disorderly development of the zones of cartilage hypertrophy, with reduced number and irregular arrangement of hypertrophic chondrocytes; similar less severe changes were present in the zones of cartilage proliferation. Histochemical staining of the cartilage matrix was variable in intensity, and there was evidence of abnormal resorption of cartilage matrix at the level of the primary spongiosa. Osteoid formation and subsequent bone remodelling seemed unaffected, and diaphyseal cortical bone appeared normal at the gross and light microscopic level. No infectious agents were identified, and other known causes for chondrodysplasia in calves were excluded. The most likely cause for the syndrome was considered to be congenital manganese deficiency. Further surveys of tissue and blood manganese levels from cows and calves with and without clinical signs from the region are planned.