Dr Alex Ford examines an amphipod shrimp similar to the infected specimens taken from Langstone Harbour.
A new species of brain-altering parasite has been discovered in Hampshire by University of Portsmouth scientists.
A study led by marine biologist Dr Alex Ford found that amphipod shrimps in Langstone Harbour, Portsmouth, were infected with worm-like parasites that changed the shrimps’ behaviour to make them swim into the light, where they were more likely to be eaten by birds.
The new species – which has not yet been named – is a type of parasite that lives inside a succession of hosts before eventually being consumed by birds. The parasite’s eggs are then expelled in the birds’ faeces, allowing a whole new life cycle to begin.
The research, published in Parasitology journal, showed that a hormone, serotonin, produced during the infection made the shrimp want to swim away from darkness and towards light.
Scientists are still investigating whether the serotonin is produced by the parasite or if the parasite’s physical presence alters the shrimp’s brain chemistry.
Serotonin is one of the chemicals that controls behaviour in all animals, including humans, but the shrimp’s response – to move towards light – seems to be unique to crustaceans.
The study, funded by the Natural Environment Research Council (NERC), mapped the population of the shrimp in the harbour over 18 months, identifying the parasite as a previously unreported species.
Dr Ford, of the University’s Institute of Marine Sciences, said: “We think we know all the species that live on our doorstep, so it’s really exciting when we find a new one. I expect that shores around the UK will be harbouring other parasites that are completely unknown to science at the moment.”
According to Dr Ford, this is only the second trematode species recorded that manipulates the behaviour of its shrimp host.
The parasite’s presence was shown by the study to have a dramatic effect on the shrimp population.
The brain-altering trematode parasite.
“When the parasite numbers go up the host numbers go down, which fits in with the idea that the parasite wants its host to be eaten, because the parasite needs to be inside a bird to complete its life cycle,” said Dr Ford.
“We did some experiments on the shrimps and gave them the choice of being in the light or dark. The ones with the parasite wanted to be in the light, whereas the ones without wanted to be in the dark.
“This is the first study to specifically measure which genes linked to serotonin have been altered by infection.”
Shrimps were made to swim towards light after infection by trematodes parasites.
Dr Ford said: “If it turns out that the parasite is actually producing a chemical that can alter brain chemistry, that has some very interesting repercussions.
“It will help us better understand the mechanisms controlling crustacean behaviour and may even help us better understand ways to regulate serotonin in humans.”
Serotonin is widely thought to be a major contributor to feelings of happiness and well-being.
The affected shrimp species is found in waters from Iceland to Portugal, but it is not yet known whether the parasite lives alongside it in all of those places.
The latest research follows a study in 2010 led by Dr Ford in which shrimps exposed to antidepressants were shown to become more attracted to light.
Eye experts in Southampton are leading UK trials of a new drug that could slow the progression of a currently untreatable form of blindness.
In a landmark study, patients at Southampton General Hospital who have suffered some visual loss as a result of geographic atrophy (GA), an advanced form of dry age-related macular degeneration (AMD), are receiving injections of lampalizumab.
It is believed the treatment, now in its final clinical trial phase, could reduce the area of damage in most sufferers by around 20% – but by 44% in some with a particular genetic feature.
The condition, which occurs when cells in the part of the eye responsible for vision become damaged by the build-up of waste deposits called drusen, causes a progressive and permanent loss of vision.
Despite accounting for 90% of all cases of AMD – the leading cause of blindness in the UK affecting around 500,000 people over the age of 50 – there are currently no approved treatments for the early, intermediate or advanced forms of dry AMD.
The remaining 10% of cases are caused by the ‘wet’ form of the disease, which develops when abnormal blood vessels appear underneath and within the retina and can lead to rapid vision loss – though it can be treated and stabilised using a class of drugs called anti-VEGF agents.
“Geographic atrophy secondary to AMD is a debilitating condition which affects around five million people worldwide and has been untreatable for a long period of time, so this study marks a major milestone for patients and clinicians,” explained Professor Andrew Lotery, a consultant ophthalmologist at Southampton General Hospital and the study’s chief investigator in the UK.
“Lampalizumab has already been shown to reduce damage caused by GA by 20% in most cases and, for some patients with a specific genetic biomarker, by up to 44% in early-stage trials.
“These are significant reductions and, if they are replicated in this larger study, it will revolutionise the way we treat the condition and mean patients are no longer condemned to blindness when diagnosed.”
The two-year project will see just under 2,000 patients enrolled onto one of two multi-national studies. Two-thirds of patients will receive a 10 mg dose of lampalizumab by intravitreal injection every four or six weeks and the other third will be treated with sham injections.
Prof Lotery, who is also a professor of ophthalmology at the University of Southampton, added: “We are still recruiting for the study, so it is important we get the message out to sufferers that they can come forward and be part of what we hope will be a very exciting development.”
Any patient with GA who would like to be considered for participation in the study can be referred to Prof Lotery’s clinic by their GP or can contact Marie Nelson, senior research sister, on 023 8120 5266 or by email at firstname.lastname@example.org
If suitable, they will be assessed in a purpose-built research clinic which has been made possible by support from the Gift of Sight Appeal (www.giftofsight.org.uk). Patients who have had previous treatment for wet AMD are not suitable for the study.