Membrane-feeding methods for the mass rearing of the bed bug Cimex lectularius and the human body louse Pediculus humanus humanus in the laboratory

Blood-sucking arthropods (e.g. lice, bedbugs, mosquitoes, fleas and ticks) have a significant impact on human health and well-being. Head lice infestation is a persistent hygiene problem worldwide. Since the 1990s, there has also been a dramatic increase in bed bug infestations globally. Particularly in light of the development of insecticide resistance in these parasites, the need to develop new products for their control has grown. At the same time, there is also a growing need for efficacy testing, on the one hand for the development of new products and active substances, and on the other hand for regulatory purposes (e.g. proof of efficacy as part of biocide authorisation under EU Regulation 528/2012). It is sensible and important to have effective means of controlling them at our disposal; however, the breeding of these blood-sucking arthropods is necessary for their development and testing. The feeding of blood-sucking arthropods on vertebrate hosts (e.g. rabbits, guinea pigs), which is stressful for the animals, constitutes an animal experiment subject to notification or authorisation under the Animal Welfare Act (TierSchG §§ 8, 8a). An animal-free method of feeding bedbugs and lice would therefore enable many research institutions to carry out important basic and applied research without the need for surrogate hosts.

The aim of the project was therefore to develop, test and establish an artificial feeding technique for the large-scale rearing of clothes lice and bedbugs without the use of vertebrate hosts. As part of this project, the breeding of bedbugs on rabbit hosts was completely discontinued. Since then, feeding has been carried out exclusively using a Hemotek® membrane feeding system with defibrinated pig’s blood. This has enabled the total number of animal experiments involving rabbits for the blood-feeding of arthropods at the Federal Environment Agency to be reduced by around 100 per year. The elimination of vertebrate hosts for feeding mass-reared bedbugs represents a breakthrough and a significant advance for bedbug research, as animal-free rearing in the laboratory enables research to be conducted in a far greater number of laboratories.

There are very few published studies on the mass rearing of head and body lice in the laboratory. To date, only body lice have been successfully bred on a long-term basis using rabbits as hosts. The mass rearing of body lice without a vertebrate host has not yet been described. This project demonstrated that it is, in principle, possible to feed body lice on a membrane using animal blood. Development across several generations has so far only been achieved using rabbit blood. The reason for this is presumably an adaptation to the rabbit host that has developed over decades; in the case of body lice from the Federal Environment Agency’s breeding programme, this has resulted in the failure of intergenerational development following feeding with other blood types (from pigs, cattle, sheep and horses). Further trials over the next two years are intended to show whether permanent mass breeding is initially possible on the membrane using defibrinated rabbit blood. The aim remains to permanently replace the rabbit host as soon as possible, in the interests of animal welfare.

Membrane feeding methods that have been tested to date include those for mosquitoes, ticks and predatory bugs, as well as for lice and bedbugs. The problem here is that existing feeding methods for bedbugs (Fig. 1) and lice (Fig. 2) are only successful for breeding and maintaining small numbers of insects over short periods. For laboratories where bedbugs and lice need to be bred continuously and in large numbers, the methods described are not practicable. They are often too labour-intensive and do not produce enough offspring to sustain a large breeding population. Furthermore, breeding failures occur, meaning that the animals must once again be fed on vertebrates. Despite occasional severe breeding failures, large numbers of bedbugs are now being fed in the 14th generation at the Federal Environment Agency using a prototype membrane feeding system (Fig. 3). The method has been continuously refined, yet it is not yet fully developed for everyday use. The feeding apparatus now being planned is intended to enable simple and straightforward feeding. Experiments on louse breeding will be carried out during the project period, as lice are suitable model organisms for head lice.