Co-existing conditions for deaths from infectious and parasitic diseases in Australia

Objective: To examine the frequency distribution of co-existing conditions for deaths where the underlying cause was infectious and parasitic diseases. Materials and methods: Besides the underlying cause of death, the distributions of co-existing conditions for deaths from infectious and parasitic diseases were examined in total and by various age and sex groups, at individual and chapter levels, using 1998 Australian mortality data. Results: In addition to the underlying cause of death, the average number of reported co-existing conditions for a single infectious and parasitic death was 1.62. The most common co-existing conditions were respiratory failure, acute renal failure non-specific causes, ischaemic heart disease, pneumonia and diabetes. When studying the distribution of co-existing conditions at the ICD-9 chapter level, it was found that the circulatory system diseases were the most important. There was an increasing trend in the number of reported co-existing conditions from 60 years of age upwards. Gender differences existed in the frequency of some reported co-existing conditions. The most common organism types of co-existing conditions were other bacterial infection and other viruses. Conclusions: The study indicated that the quality of death certificates is less than satisfactory for the 1998 Australian mortality data. The findings may be helpful in clarifying the ICD coding rules and the development of disease prevention strategies. (C) 2003 International Society for Infectious Diseases. Published by Elsevier Ltd. All rights reserved.

Treating liver disease in the avian patient

The liver plays a major role in the body's metabolism and, as such, is subject to a multitude of insults-infectious, toxic, metabolic, nutritional, traumatic, and neoplastic. Consequently, liver disease is not uncommon in avian and other exotic patients. As diagnostic modalities (and our experience in using them and interpreting them) improve, veterinarian are becoming more aware of the presence of (often subclinical) liver disease in their patients, and often of the specific nature of that disease. Through new research, veterinarians also are more able to appreciate the liver's unique function and metabolism and the role it plays in the function of the body as a whole. This understanding has led to a better awareness of how the liver responds to disease, and this has allowed refinements in the treatment of diseased and damaged livers. However, treating liver disease is not just about treating the organ; the patient as a whole must be supported and treated until a successful resolution has been achieved. Treatment therefore must be aimed at supporting the patient, treating the specific condition, and creating an environment that allows the liver to heal and regenerate. This article briefly reviews the anatomy and physiology of the liver and how it responds to insult. Treatment of liver disease then is discussed using the aims described above. (C) 2004 Elsevier Inc. All rights reserved.

Reflecting on ethical and legal issues in wildlife disease

Disease in wildlife raises a number of issues that have not been widely considered in the bioethical literature. However, wildlife disease has major implications for human welfare. The majority of emerging human infectious diseases are zoonotic: that is, they occur in humans by cross-species transmission from animal hosts. Managing these diseases often involves balancing concerns with human health against animal welfare and conservation concerns. Many infectious diseases of domestic animals are shared with wild animals, although it is often unclear whether the infection spills over from wild animals to domestic animals or vice versa. Culling is the standard means of managing such diseases, bringing economic considerations, animal welfare and conservation into conflict. Infectious diseases are also major threatening processes in conservation biology and their appropriate management by culling, vaccination or treatment raises substantial animal ethics issues. One particular issue of great significance in Australia is an ongoing research program to develop genetically modified pathogens to control vertebrate pests including rabbits, foxes and house mice. Release of any self-replicating GMO vertebrate pathogen gives rise to a whole series of ethical questions. We briefly review current Australian legal responses to these problems. Finally, we present two unresolved problems of general importance that are exemplified by wildlife disease. First, to what extent can or should 'bioethics' be broadened beyond direct concerns with human welfare to animal welfare and environmental welfare? Second, how should the irreducible uncertainty of ecological systems be accounted for in ethical decision making?

Exposing extinction risk analysis to pathogens: Is disease just another form of density dependence?

In the United States and several other countries., the development of population viability analyses (PVA) is a legal requirement of any species survival plan developed for threatened and endangered species. Despite the importance of pathogens in natural populations, little attention has been given to host-pathogen dynamics in PVA. To study the effect of infectious pathogens on extinction risk estimates generated from PVA, we review and synthesize the relevance of host-pathogen dynamics in analyses of extinction risk. We then develop a stochastic, density-dependent host-parasite model to investigate the effects of disease on the persistence of endangered populations. We show that this model converges on a Ricker model of density dependence under a suite of limiting assumptions, including. a high probability that epidemics will arrive and occur. Using this modeling framework, we then quantify: (1) dynamic differences between time series generated by disease and Ricker processes with the same parameters; (2) observed probabilities of quasi-extinction for populations exposed to disease or self-limitation; and (3) bias in probabilities of quasi-extinction estimated by density-independent PVAs when populations experience either form of density dependence. Our results suggest two generalities about the relationships among disease, PVA, and the management of endangered species. First, disease more strongly increases variability in host abundance and, thus, the probability of quasi-extinction, than does self-limitation. This result stems from the fact that the effects and the probability of occurrence of disease are both density dependent. Second, estimates of quasi-extinction are more often overly optimistic for populations experiencing disease than for those subject to self-limitation. Thus, although the results of density-independent PVAs may be relatively robust to some particular assumptions about density dependence, they are less robust when endangered populations are known to be susceptible to disease. If potential management actions involve manipulating pathogens, then it may be useful to. model disease explicitly.

Real-time reverse transcriptase PCR for the endogenous koala retrovirus reveals an association between plasma viral load and neoplastic disease in koalas

Koala retrovirus (KoRV) is a newly described endogenous retrovirus and is unusual in that inserts comprise a full-length replication competent genome. As koalas are known to suffer from an extremely high incidence of leukaemia/lymphoma, the association between this retrovirus and disease in koalas was examined. Using quantitative real-time reverse transcriptase PCR it was demonstrated that KoRV RNA levels in plasma are significantly increased in animals suffering from leukaemia or lymphoma when compared with healthy animals. Increased levels of KoRV were also seen for animals with clinical chlamydiosis. A significant positive association between viral RNA levels and age was also demonstrated. Real-time PCR demonstrated as much as 5 log variation in KoRV proviral DNA levels in genomic DNA extracted from whole blood from different animals. Taken together these data indicate that KoRV is an active endogenous retrovirus and suggests that it may be causally linked to neoplastic disease in koalas.

Vaccine trial as “probe” to define the burden of pneumococcal pneumonia disease [Comment]

In today's Lancet, Felicity Cutts and colleagues present their findings on the randomised double-blind placebo controlled trial on the efficacy of a nine-valent pneumococcal conjugate-vaccine (9PCV) against radiologically confirmed pneumonia and invasive pneumococcal disease in children immunised before 12 months of age in The Gambia. The study site is a rural African setting with high child-mortality, a low prevalence of HIV-1 infection in pregnant mothers, and with endemic malaria. The authors report a vaccine efficacy of 37% (95% CI 27–45%) against first-episodes of radiological pneumonia in a per-protocol analysis. Intention-to-treat analysis showed similar results. The investigators also found that the vaccine could significantly reduce the incidence of vaccine-type invasive pneumococcal disease by 77%, by 50% for all-serotype invasive pneumococcal disease, by 15% for all-cause health-facility admissions, and by 16% for overall child mortality.

Identifying health centers in Honduras infested with Rhodnius prolixus using the seroprevalence of Chagas disease in children younger than 13 years

The objective of this study is to determine if a Chagas disease protocol starting with a serological survey is as reliable at identifying insect-infested areas as one using the gold standard entomological survey. The study found that health center areas infested with Rhodnius prolixus were identified using a threshold seroprevalence of 0.1%. The serological survey took half the time and was 30% less expensive than the entomological survey. Developing countries with limited resources may find this strategy useful in combating Chagas disease. This strategy also identifies seropositive children, which facilitates their treatment.

Survival of rabbit haemorrhagic disease virus (RHDV) in the environment

A study was conducted to investigate the persistence of rabbit haemorrhagic disease virus (RHDV) in the environment. Virus was impregnated onto two carrier materials (cotton tape and bovine liver) and exposed to environmental conditions on pasture during autumn in New Zealand. Samples were collected after 1, 10, 44 and 91 days and the viability of the virus was determined by oral inoculation of susceptible 11- to 14-week-old New Zealand White rabbits. Evidence of RHDV infection was based on clinical and pathological signs and/or seroconversion to RHDV. Virus impregnated on cotton tape was viable at 10 days of exposure but not at 44 days, while in bovine liver it was still viable at 91 days. The results of this study suggest that RHDV in animal tissues such as rabbit carcasses can survive for at least 3 months in the field, while virus exposed directly to environmental conditions, such as dried excreted virus, is viable for a period of less than I month. Survival of RHDV in the tissues of dead animals could, therefore, provide a persistent reservoir of virus, which could initiate new outbreaks of disease after extended delays.