Transmission dynamics and optimal control of H7N9 in China

H7N9 avian influenza is a highly pathogenic zoonotic disease. In order to control the disease, many strategies have been adopted in China such as poultry culling, the closure of live poultry markets (LPMs), the vaccination of poultry, and the treatment for humans. Due to the limited resource, it is of paramount significance to achieve the optimal control. In this paper, an epidemic model incorporating the selective culling rate is formulated to investigate the transmission mechanism of H7N9. The threshold dynamics and bifurcation analyses of the model are well investigated. Furthermore, the problem of optimal control is explored in line with Pontryagin’s Maximum Principle, with consideration given to the comprehensive measures. The numerical simulations suggest that the vaccination of poultry and the closure of LPMs are the two most economical and effective measures.

Hunting the hunter: using genetic profiling for improved management of shark attacks on humans

DNA evidence is routinely used to identify individual predators responsible for attacks on people and livestock in terrestrial settings. However, the use of transfer DNA techniques in aquatic environments20 for similar purposes is a recent development. To date, DNA barcoding has been used successfully to identify shark species depredating fish catches and biting surfboards and neoprene surfaces. In this study we demonstrate the successful DNA barcoding and fingerprinting of individual sharks from transfer DNA collected directly from the wounds of two shark bite victims. The successful use of DNA techniques to identify both species and specific individuals responsible for shark bites opens the door to selective removal of these individuals as an innovative shark bite risk management strategy. This selective approach would be a more effective, eco-responsible, cost-effective and ethical solution for vulnerable taxa than ongoing non-selective culling campaigns.

Economics of respiratory disease in dairy replacement heifers

Bovine respiratory disease (BRD) is a frequent disease concern in dairy cattle and is most commonly diagnosed in young dairy heifers. The impact of BRD is highly variable, depending on the accuracy and completeness of detection, effectiveness of treatment, and on-farm culling practices. Consequences include decreased rate of weight gain, a higher culling risk either as heifers or as cows, delayed age at first service, delayed age at first calving, and in some cases, lower future milk production. In this data set of 104,100 dairy replacement heifers from across the USA, 36.6% had one or more cases diagnosed within the first 120 days of age with the highest risk of new cases occurring prior to weaning. Comparison of the raising cost for heifers with BRD and those without a recorded history of BRD resulted in an estimated cost per incident case occurring in the first 120 days of age of $252 or $282, depending upon whether anticipated future milk production differences were considered or not. Current market conditions contributed to a cost estimate that is significantly higher than previously published estimates, driven in part by the losses associated with selective culling of a subset of heifers that experienced BRD.

How Vanhu Managed Tsetse

This chapter shows that vanhu vatema understood mobility as the centerpiece of their interactions with the insect. It commences from a view of vatema's management of mhesvi as a site of innovation, illustrating the centrality of mobility in interactions between vanhu and zvipukanana. The chapter strategically deploys the travel accounts of vachana writing in the nineteenth century about their encounters with people living with and despite mhesvi. The strategy herein is to read these travel accounts as acts of witnessing to, and confessions about, ruzivo rwemhesvi (knowledge of tsetse) among the people living in the lands between and along the Zambezi and Limpopo Rivers. The chapter maps mhesvi-infested areas and mhesvi management techniques—namely, forest clearance, selective culling of mhuka, strategic settlement of vanhu, use of repellents, movement by night, and inoculation. At the end of the day, African mhesvi management was about mobilities management.

Tusklessness and tusk fractures in free-ranging African savanna elephants (Loxodonta africana)

The incidence of tusklessness varies between free-ranging African elephant populations. Sex-linked genetic drift predicts 2 outcomes - the condition becomes fixed and sex-specific incidences diverge when populations are small and/or heavily poached. By contrast, for large and intact populations, tusklessness diminishes and there is no variation between sexes. We tested these predictions by comparing sex-specific incidences between 15 populations: a small one with a skewed founder effect towards tusklessness; 5 that had experienced intense levels of poaching; 2 that had been subjected to non-selective culling and 7 that are relatively pristine. Patterns of rainfall were studied of tusk fractures amongst these populations to correct for any effect that acquired tusklessness may have on our predictions. The incidence of tusk fractures was related to annual rainfall, but the mechanism that leads to an increase of the condition in drier areas was not clear. Incidences of tusk fractures in free-ranging populations implied that the frequency of acquired bilateral tusklessness is low and should not affect our results. All males had tusks. Tusklessness in females was high in the small skewed founder population and some of those where there was a history of poaching. The incidence is expected to decline if the residual population is large.