A perspective on SIDS pathogenesis. The hypotheses: plausibility and evidence

Several theories of the underlying mechanisms of Sudden Infant Death Syndrome (SIDS) have been proposed. These theories have born relatively narrow beach-head research programs attracting generous research funding sustained for many years at expense to the public purse. This perspective endeavors to critically examine the evidence and bases of these theories and determine their plausibility; and questions whether or not a safe and reasoned hypothesis lies at their foundation. The Opinion sets specific criteria by asking the following questions: 1. Does the hypothesis take into account the key pathological findings in SIDS? 2. Is the hypothesis congruent with the key epidemiological risk factors? 3. Does it link 1 and 2? Falling short of any one of these answers, by inference, would imply insufficient grounds for a sustainable hypothesis. Some of the hypotheses overlap, for instance, notional respiratory failure may encompass apnea, prone sleep position, and asphyxia which may be seen to be linked to co-sleeping. For the purposes of this paper, each element will be assessed on the above criteria

Reclassification of SIDS cases - a need for adjustment of the San Diego classification?

A study was undertaken reclassifying cases of sudden infant death syndrome (SIDS) taken from two geographically separate locations utilizing the San Diego definition with subclassifications. One hundred twenty-eight infant cases were examined from files at Forensic Science South Australia in Adelaide, SA, Australia over a 7.5-year period from July 1999 to January 2007. Thirty-one cases (24%) had initially been diagnosed as SIDS and 30 (23%) as undetermined while 67 (52%) had an explainable cause of death. After reclassification, the number of SIDS cases had increased to 49 of the 128 cases, now representing 38% of the cases; category IB SIDS constituted 10 (20%) and II SIDS 39 (80%) of the SIDS cases. No cases were classified as IA SIDS. Two hundred eighteen infant cases were identified from the files of the Department of Forensic Medicine, Aarhus University, Denmark over a 16-year period from 1992 to 2007. Eighty-two (38%) were originally diagnosed as SIDS, 128 (59%) with identifiable causes of death, and 8 (4%) as unexplained. After review, 77 (35%) cases were reclassified as SIDS, a decrease of 6%. Twenty (26%) infants were classified as category IB SIDS and 57 (74%) as II SIDS. None of the cases met the criteria for IA SIDS. Problems arose in assessing cases with failure to thrive, fever, and possible asphyxia. Modifications to the San Diego subclassifications might improve the consistency of categorizing these cases.Lisbeth Lund Jensen, Marianne Cathrine Rohde, Jytte Banner, Roger William Byar

Pathogen surveillance and epidemiology in endangered peninsular bighorn sheep (Ovis canadensis nelsoni)

Peninsular bighorn sheep (Ovis canadensis nelsoni) are found exclusively in Southern California and Baja Mexico. They are federally endangered due to multiple threats, including introduced infectious disease. From 1981 to 2017, we conducted surveillance for 16 pathogens and estimated population sizes, adult survival, and lamb survival. We used mixed effects regression models to assess disease patterns at the individual and population levels. Pathogen infection/exposure prevalence varied both spatially and temporally. Our findings indicate that the primary predictor of individual pathogen infection/exposure was the region in which an animal was captured, implying that transmission is driven by local ecological or behavioral factors. Higher Mycoplasma ovipneumoniae seropositivity was associated with lower lamb survival, consistent with lambs having high rates of pneumonia-associated mortality, which may be slowing population recovery. There was no association between M. ovipneumoniae and adult survival. Adult survival was positively associated with population size and parainfluenza-3 virus seroprevalence in the same year, and orf virus seroprevalence in the previous year. Peninsular bighorn sheep are recovering from small population sizes in a habitat of environmental extremes, compounded by infectious disease. Our research can help inform future pathogen surveillance and population monitoring for the long-term conservation of this population