Development of a Technique Using Artificial Membrane for In Vitro Rearing of Body Lice Pediculus humanus humanus

TL;DR

Researchers developed a new method to rear body lice on an artificial membrane, which could replace using live animals for studying lice-borne diseases.

Contribution

A novel in vitro lice-rearing technique using an artificial membrane was developed and successfully produced one generation of body lice.

Findings

Lice reared on heparinized blood in a Petri dish reached adulthood in 21 days and produced 52 eggs.

In vitro lice showed comparable feeding and longevity to those reared on rabbits, though fecundity was lower.

The artificial membrane method met animal welfare requirements and could replace animal models in biological assays.

Abstract

Louse-borne diseases have caused millions of deaths around the world and are currently re-emerging in some countries. Implementing a simple and accessible lice-rearing system would significantly advance research on the louse–pathogen cycle and vectorial capacities. Several in vivo and in vitro lice-rearing methods have been developed. However, these approaches have drawbacks, making lice production more difficult. Here, we aimed to adapt the Orlando (Or) strain of body lice on an artificial membrane. The Hemotek system and a Petri dish system covered with a Parafilm membrane were tested on newly hatched first-stage larvae (L1). Rearing follow-up consisted of recording dead, fed and moulted specimens throughout the experiments. In addition, microscopic ultra-structures, blood meal digestion and sterility were evaluated and compared to those of larvae being reared on rabbit hosts. When using heparinised blood on a Petri dish, we were able to maintain one generation of body lice. Development into adulthood was recorded 21 days after hatching, and 52 eggs were deposited. Inspection of the blood meal revealed a colour difference among lice fed in vitro and in vivo, while microscopic investigations did not show any differences. The in vitro lice-rearing experiments were conducted in accordance with animal welfare requirements and therefore have the potential to replace animal models in various biological assays.

Human lice are the only hematophagous ectoparasites specific to human hosts. They transmit epidemic typhus, trench fever and relapsing fever, diseases which have already caused millions of deaths worldwide. In order to further investigate lice vectorial capacities, laboratory-controlled live lice colonies are essential. Previously developed lice-rearing methods significantly advanced research on louse-borne diseases and louse biology. In this study, we aimed to develop a rearing technique for the Orlando (Or) strain of body lice on an artificial membrane. We tested two systems, namely the Hemotek feeding system and a Petri dish with the lice being fed through a Parafilm membrane. Lice longevity and development were drastically affected by the blood anticoagulant. Additionally, heparinised human blood on a Petri dish was the best candidate when compared to the control group (reared on a rabbit). Therefore, this strategy was applied to 500 lice. Development into adulthood was recorded after 21 days (17 days for the rabbits), and 52 eggs were deposited (240 for the rabbits). In this study, we were able to maintain one generation of body lice on an artificial membrane with comparable feeding and longevity rates to those fed on live rabbits. However, lice fecundity decreased on the artificial membrane. In vitro lice-rearing experiments will enable pathogen infection assays and pesticide bioassays to be carried out in accordance with animal welfare requirements.

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