Recently, I received an email enquiry from a researcher developing techniques for replacement models of arthropod vectors of infectious disease. Arthropod vectors include midges, mosquitos, ticks, fleas, and other not-so-popular animals, who are responsible for the transmission of diseases infecting both humans and non-human animals. These diseases can be viral, bacterial, or parasitic – the more obvious would be mosquito-transmitted malaria or Lyme disease from ticks. The effect of global climate change, wildlife migration, and increased surveillance, means that there is strong evidence that temperate regions, such as the UK, are now seeing repeated introductions of mosquito species, as well as mosquito-borne viruses, not previously detected in the UK.

What all these bugs have in common is that they require biting another animal (including us!) to get blood meals needed for their eggs to develop and hatch to produce the next generation. It is this blood feeding and reproduction cycle that has been hijacked by the disease agent(s), like Plasmodium falciparum (malaria), or spirochete bacterium, Borrelia burgdorferi, responsible for Lyme disease.   

Although we may be primarily concerned by how something like Lyme disease affects humans, it also affects animals who become a ‘reservoir’ for human infection. Research into these kinds of diseases therefore needs to focus on different aspects: the disease agent, the vector, the animal infection and the human infection, which requires different specialisms. 

It’s not just for us humans

Working with arthropod vectors of infectious disease also adds another layer of complexity to the replacement issue. Historically, research insectaries have raised colonies of these bugs fed on the blood of other animals, to study the mechanisms and spread of the diseases and how they affect their host species, whether human or animal. 

So there is another level (or two!) of replacement that are required in these disease systems:  

1.  replacing the arthropod vector 

1. replacing the animals used to feed the bugs 

1. and those who are the target hosts of the disease agent.   

Teaching and training

Replacements of animals in bioscience education have been established for decades and can vary in complexity from elegant origami alternatives to dissection in Schools, or 3D models, to using ‘haptic’ simulators in veterinary or surgical training. The incredible work by InterNICHE beautifully demonstrates how humane, innovative techniques can fully replace animals and enhance knowledge and skills acquisition in veterinary training.  

Alternatives to animals when it’s for the sake of the animals?

Arthropod-borne diseases are the cause of some of the greatest burdens to both human and animal health worldwide. But what about replacing animals in research that’s just for the animals*? Our organisation chooses to focus on removing the animal element of research for human health, but many of the techniques we discuss as replacements in human research – like organs-on-a-chip, organoids and spheroids – are equally applicable to veterinary science, although veterinary applications are lagging behind human research.    

Replacement is needed in so many different areas

We can only provide a tiny drop in the ocean of funding available to researchers working on developing and applying non-animal methods in human research. Do you think focusing on human-relevant research is the right way to spend our donors’ money, or do you think we should broaden our horizons a little? We’d appreciate your thoughts on this! 

*some might argue that no veterinary research is just for the animals, but rather for the humans who benefit from the animals’ continued health and wellbeing – but this is the subject of a much more controversial blog!