Estimating disease transmission in wildlife, with emphasis on leptospirosis and bovine tuberculosis in possums, and effects of fertility control

Marsupial Cooperative Research Centre at Landcare Research, Private Bag 11052, Palmerston North 5301, New Zealand; and; Applied Ecology Group, University of Canberra, ACT 2601, Australia
Journal of Applied Ecology (Impact Factor: 4.75). 04/2002; 38(6):1362 - 1370. DOI: 10.1046/j.0021-8901.2001.00676.x

ABSTRACT Summary • We present methods for estimating disease transmission coefficients in wildlife, using Leptospira interrogans infection (a bacterial disease transmitted predominantly during social contacts) in brushtail possums Trichosurus vulpecula as a model system. • Using data from a field experiment conducted on a naturally infected possum population, we estimated disease transmission coefficients assuming either ‘density-dependent’ or ‘frequency-dependent’ transmission. • A model-selection approach determined that density-dependent transmission was the most appropriate form of the transmission of L. interrogans infection in brushtail possums. • We used the chosen model of transmission to examine experimentally the effect of tubally ligating female brushtail possums on the epidemiology of L. interrogans. The estimated transmission coefficient was 28% higher (P = 0·16) in populations subject to tubal ligation, raising the possibility that fertility control of this type may increase disease transmission rates. • Altering mating behaviour through fertility control may have the potential to control diseases such as bovine tuberculosis in brushtail possums, although the potential of fertility control techniques to change disease transmission coefficients and disease epidemiology requires further investigation. This would require models that examine the combined effects of fertility control on population dynamics, social behaviour and disease transmission coefficients simultaneously.

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    ABSTRACT: Leptospirosis is an endemic disease in Malaysia and recently has received increasing attention mainly due to several recent incidents that have resulted in human mortality which have alarmed health professionals in Malaysia. The increasing incidence of leptospirosis in forested regions is associated with the bacteria infecting small wild mammals other than rats. Infection in wildlife could result in the introduction of new serovars to humans and domesticated animals. More research on leptospirosis and the screening of wildlife and humans near wildlife habitats is required to have a better understanding of the involvement of wildlife in the disease.
    The Malaysian journal of pathology 12/2013; 35(2):123-32.
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    ABSTRACT: Summary • Information on close interactions between wild animals is difficult to obtain for cryptic species, but is important for understanding their social and mating systems as well as the dynamics of directly transmitted diseases. • The persistence of bovine tuberculosis (Tb) in New Zealand is enhanced by the presence of wildlife hosts for the infection, principally the brushtail possum Trichosurus vulpecula. Quantifying the relationship between the frequency of contacts and possum population density is important for understanding the dynamics of the disease and the potential effectiveness of different methods for disease control. • We used novel proximity data loggers to record contacts (• Most contacts between male and female possums appeared to be sexual in nature, and contact rate was not related linearly to population density. Contacts occurred more frequently during the breeding season, when a female possum could interact with up to four males. However, even during this peak contact period the average contact rate was equivalent to only one contact every 2 days. • The total duration of contacts was significantly higher during the breeding season. During this time, contacts lasting for more than 1 min occurred episodically. A small proportion (2·3%) of the interactions lasted for 5–15 min, although the mean duration of contacts was only 18–26 s 24 h−1. Outside the breeding season, contacts were brief and infrequent. • The frequency of contacts showed a slight increase when the possum density increased sharply at the main study site, although the duration of contacts was unaffected. This increase in contact rate may have been the result of an influx of new animals causing perturbation to the existing population. • Previous paternity analysis using DNA profiling indicated that the possum mating system is polygynous, with males being promiscuous. Our data reveal that females are probably also promiscuous and that the mating system of possums may therefore be polygamous, including both polygyny and polyandry. • Synthesis and applications. Most contacts between possums occur in the peak mating season and appear to be related to mating and associated behaviour. There are some contacts outside the main mating season, but these are infrequent. The transmission of bovine Tb infection in possum populations may therefore occur by other routes in addition to direct contact. The non-linear (frequency-dependent) contact rate–density relationship recorded provides some insight as to why repeated population reduction is necessary to achieve lasting Tb control in possum populations. It also provides some support for the role that could be played by sexually transmitted, viral-vectored immunocontraception in the control of possum populations, either alone or in conjunction with more traditional control methods. Journal of Applied Ecology (2005) 42, 595 –604 doi: 10.1111/j.1365-2664.2005.01026.x
    Journal of Applied Ecology 06/2005; 42(3). · 4.75 Impact Factor
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    Theriogenology 01/2013; · 1.85 Impact Factor


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