Modeling the Effect of Population Dynamics on the Impact of Rabbit Hemorrhagic Disease

Abstract:  The European wild rabbit ( Oryctolagus cuniculus ) is a staple prey species in Mediterranean ecosystems. The arrival and subsequent spread of rabbit hemorrhagic disease throughout southwestern Europe, however, has caused a decline in rabbit numbers, leading to considerable efforts to enhance wild rabbit populations, especially through habitat management. Because rabbit population dynamics depend on habitat suitability and changes in habitat structure and composition subsequent to habitat management, I evaluated the effects of population dynamics on the long-term impact of rabbit hemorrhagic disease on rabbit populations. I used an age-structured model with varying degrees of population productivity and turnover and different habitat carrying capacities, and I assumed the existence of a unique, highly pathogenic virus. My results suggest that disease impact may be highly dependent on habitat carrying capacity and rabbit population dynamics, and the model provided some insight into the current abundance of wild rabbits in different locations in southwestern Europe. The highest disease impact was estimated for populations located in habitats with low to medium carrying capacity. In contrast, disease impact was lower in high-density populations in habitats with high carrying capacity, corresponding to a lower mean age of rabbit infection and a resulting lower mortality from rabbit hemorrhagic disease. The outcomes of the model suggest that management strategies to help rabbit populations recover should be based on improving habitats to their maximum carrying capacity and increasing rabbit population productivity. In contrast, the use of strategies based on temporary increases in rabbit density, including vaccination campaigns, translocations, and temporal habitat improvements at medium carrying capacities, may increase disease impact, resulting in short-term decreases in rabbit population density.     

Management of red cell alloimmunisation in pregnancy: the non-invasive monitoring of the disease

Haemolytic disease of the fetus and newborn (HDFN) due to red cell alloimmunization was a significant cause of fetal and neonatal morbidity and mortality until the introduction of anti-D immunoglobulin, which has dramatically changed the incidence of the disease. However, it is still a major problem in affected pregnancies. The emphasis of current clinical management has shifted from an invasive approach to non-invasive monitoring of the disease. The key elements of the modern management are determining which fetuses are at risk of HDFN with the use of cell-free fetal DNA in maternal plasma (fetal RHD genotype) and the follow-up of antigen positive fetuses by Doppler ultrasonography to detect anaemia severe enough to need treatment. When anaemia is suspected, an invasive approach is still required in a timely manner for confirmation of the degree of anaemia and to administer blood transfusions. This non-invasive approach prevents unnecessary administration of human-derived blood products, with the consequent ethical and cost implications and most importantly avoids iatrogenic conversion of mild to severe disease by avoiding need for techniques such as amniocentesis. The potential problem of the non-invasive approach is the reduction in the total number of invasive procedures, with the subsequent difficulty of maintaining the skills required to perform them. Copyright © 2010 John Wiley & Sons, Ltd.