Oxitec Newsletter December 2013

December 17, 2013

NEWSLETTER December 2013

Oxitec in Brazil: mosquito control in Jacobina

I’m Dr Amandine Collado, senior scientist at Oxitec providing technical support to Moscamed, a Brazilian Social Organization recognised by the Ministry of Agriculture and Bahia State (http://www.moscamed.org.br/2012/moscamed.php). Releases by Moscamed of Oxitec’s OX513A transgenic strain of the dengue mosquito, Aedes aegypti, in 2011 and 2012 in the neighbourhoods of Mandacaru and Itaberaba village resulted in suppression of the wild populations by 85% and 96%, respectively. The last time I wrote an article for the Oxitec newsletter, Moscamed was conducting extensive public engagement activities in the town of Jacobina, where I am now helping them target the dengue mosquito through releases of Oxitec mosquitoes.

Jacobina, which has around 50,000 inhabitants, is one of the cities most affected by dengue in Bahia state. In 2009, 1,534 cases of dengue were reported, and the number of cases remained over 200 in 2010 and 2011, when conventional dengue vector control measures were taking place. Unfortunately, dengue cases were on the rise again in 2012 with 1,647 cases, and two deaths by dengue haemorrhagic fever.

With such a critical situation, Moscamed was asked to help control the dengue vector in Jacobina. In response, their production facility (Unidade Projeto Aedes Transgênico  – UPAT) is producing 500,000 transgenic male mosquitoes every week under the supervision of Michelle Pedrosa. The first releases started last June in two neighbourhoods of Jacobina, Pedra Branca and Catuaba. A month and a half into this phase, our monitoring of ovitraps (which attract egg-laying wild females) has indicated that 80% of the eggs laid were fathered by the transgenic male mosquitoes that we have released: a strong indication that our males are doing their job in mating most of the wild females, a first step towards suppression of the dengue mosquito population.

These are promising results but how are Jacobinians living with the transgenic mosquito releases? “They are male mosquitoes” is the refrain that Luiza Garziera (Moscamed mosquito field supervisor) and Iana Lima (Moscamed  Public Relations) are repeating to locals “and male mosquitoes don’t bite”. “They know that these mosquitoes are doing a useful job” Iana tells me. When interviewed, locals will answer: “Well, the bug they release is a transgenic male mosquito and it doesn’t bite. He’s gonna make love to the female and their babies will die”. The message is simple but everybody understands what this is all about. Children are regularly being taught the difference between the male and female mosquitoes at schools with public health officers and Moscamed staff. “We are just getting very promising preliminary results in the first two neighbourhoods in Jacobina. We will gradually treat the rest of the 19 districts of Jacobina with Oxitec transgenic males and, in time, will achieve success!” declares Moscamed President Aldo Malavasi.

Moscamed is leading this challenging project in Jacobina, Bahia, ten times bigger than the previous target sites combined. And I feel privileged to be involved in this exciting project.

North-eastern Brazil is full of potential, with a great ambience and excellent food. Tourism needs developing and controlling the dengue vector will help this for sure! I love living here: the average temperature is 25°C and I enjoy going to the beautiful Rodeadouro river island near Juazeiro where you can eat delicious fish dishes and drink ice-cold beer in the “Solzão Nordestino” (translation: Crazily Sunny North East Brazil).

Brazil

UPAT (Unidade Projeto Aedes Transgênico) mosquito factory team, with Michelle Pedrosa (middle front) as the team supervisor.

Moscamed staff member Marcos releasing Oxitec male mosquitoes in Jacobina.

Moscamed staff member Marcos releasing Oxitec male mosquitoes in Jacobina.

Dengue and the Indian sub-continent

The global rise in dengue prevalence over recent decades has been well-charted and the Indian sub-continent has suffered as much as anywhere. Although inaccurate case reporting from this region has frequently been highlighted, a recent publication in the journal ‘Nature’ suggested that during 2010 there were around 390 million cases globally, and that India alone contributed 34% (33 million) of this total.1

The dengue virus is present in four different forms (or ‘serotypes’), each of them capable of inducing illness. When sequentially infecting the same individual, serotype combinations are considered largely responsible for the more severe forms of dengue – dengue shock syndrome (DSS) and dengue haemorrhagic fever (DHF). This adds a layer of complexity to dengue epidemiology and can result in fluctuations in the burden of the disease in a given region. With no vaccine available, reducing or preventing exposure to the virus is a primary focus. Exposure comes from the bite of infected female Aedes mosquitoes, primarily from Aedes aegypti. Male mosquitoes do not blood-feed and so cannot transmit this disease.

Across most of the tropics, control of dengue mosquitoes is increasingly difficult; rising urbanisation, travel and trade, escalating costs of insect control, and ubiquitous resistance to chemical insecticides are just some of the confounding factors. For India in particular, high rates of population growth are a serious constraint. A rapidly increasing population, primarily associated with the lower social classes, is stretching infrastructure and resources. Over 70% of Indian people live in rural areas but as these communities become poorer, more and more people are moving to large cities and living in slums with little electricity or piped water. Poor access to the latter promotes the use of domestic water containers, which along with a widening use of plastic and disposable packaging, and expanding numbers of construction sites, has increased the number of breeding sites available to mosquitoes in these urban landscapes, fuelling an increase in dengue transmission. The dengue outbreak in 2012 resulted in a sharp rise in DSS and DHF cases, and hospitals in the worst-affected states – Tamil Nadu, Kerala, Andhra Pradesh, Maharashtra, and Bengal – struggled to cope with the number of affected patients. The epidemic in 2013 is being described by the Ministry of Health as the worst in 6 years.

Only recently in neighbouring Pakistan, an health emergency was declared following an outbreak of dengue in Khyber Pakthunkhwa province led to over 6000 suspected cases of dengue, with 23 fatalities. In 2011, an outbreak in Pakistan’s second largest city, Lahore, infected more than 21,000 people, of whom 362 people died. Similarly, in Sri Lanka and Bangladesh, dengue remains a major public health problem, with regular epidemics leading to widespread suffering.

Despite these difficulties, solid progress in the fight against dengue in terms of clinical management is being made on the Indian sub-continent. Sri Lanka has amassed experience and an infrastructure that is now providing significant advances in the clinical management of the disease. Precisely structured monitoring, palliative care and fluid management are reducing the necessity for blood transfusions and minimising the worsening of individual cases.

Further encouragement has been provided by Oxitec’s Aedes aegypti control technology, which in Brazil and the Caribbean has proven capable of bringing even severe infestation levels of the mosquito under control. Results from mating studies in India have shown full compatibility of Oxitec’s transgenic Aedes aegypti with a range of counterparts from different parts of the subcontinent. As a pro-active strategy integrated with conventional vector control techniques, adoption of the Oxitec approach could provide long-term suppression of this pervasive and difficult-to-control dengue vector. In combination with the advancing clinical management, this region could benefit from a level of protection that has for many years appeared unattainable.

In India Oxitec is working with Gangabishan Bhikulal Investment and Trading Limited (GBIT). Its founder and Chairman, Dr BR Barwale, is a World Food Prize laureate, Padma Bhushan Award winner and founder of the the Barwale Foundation in India whose mission is to promote research, technology and knowledge in agriculture, health care and education for human welfare.

1Bhatt et al., (2013). The global distribution and burden of dengue. Nature: doi:10.1038/nature12060

 

A typical scene near an Indian household, with a large number of water containers, in which the dengue fever mosquito will readily breed.

A typical scene near an Indian household, with a large number of water containers, in which the dengue fever mosquito will readily breed.

Our year in publications

We work hard to make our science available to the public, and doing so in peer-reviewed publications means that they are held up for close scrutiny by fellow scientists before going to print. It has been a very busy year at Oxitec, with a wide range of research being carried out in our laboratories and in collaborations around the world, and the results published in some notable papers.

We have broken new ground in developing strains of moths that allow large-scale production of male-only groups of moths. By mass-producing males of the cotton pest, pink bollworm, and the pest of brassicas (e.g. cabbage and broccoli), diamondback moth, we can avoid co-releases of both sexes: in effect, this allows our moths to find wild females without distraction, increasing the efficiency of the pest management effect. This work was published in the journal, ACS Synthetic Biology, and was followed by a paper describing the results of our collaboration with the Shanghai Institute of Plant Physiology and Ecology, in China. Published in the high-profile Proceedings of the National Academy of Sciences, USA, it describes development of similar ‘sexing strains’ of the domestic silk moth. Instead of helping with pest management, this application of Oxitec’s genetic technology seeks to provide silk farmers with a higher-quality silk.

With a view to understanding the impact on wild predators of releasing our transgenic mosquitoes, our collaborators at the Institute for Medical Research, in Malaysia, conducted feeding studies on two other mosquito species, the young of which feed on small aquatic creatures (such as the young larvae of our mosquitoes). Results showed that our mosquitoes are not harmful to predators, underlining the low ecological impact of our species-specific pest management approach. Meanwhile, experiments at the Institut Pasteur, in Paris, showed that our transgenic male mosquitoes were able mate females as successfully as non-transgenic males in the lab, one reason for the field success of these mosquitoes. In Brazil, our dengue mosquito strain is the subject of on-going field assessment, and the results of the first such trials there – in which the target mosquito population was reduced by 85% in a town called Mandacaru – have been formally written and is now in review. We hope that this paper will be published in early 2014.

In our first foray into malaria vector control, our collaboration with the University of California, yielded a strain of one of the major malaria-transmitting mosquito in the Indian subcontinent, Anopheles stephensi. Using Oxitec’s genetics, the University of California scientists have generated mosquitoes that show flightlessness in females, a trait that results in viable males only. In mating-based mosquito control, releasing males only is key, is the females bite and transmit disease.

For an introduction to the use of genetics for mosquito control, or an update in the state of the art, two review papers – one in the journal Annual Review of Entomology and the other in Pathogens and Global Health – have also come out this year that provide excellent summaries of the different genetic technologies being developed for control of mosquitoes, not least Oxitec’s approach.

Feeding studies with our mosquitoes in the laboratory have complemented our field work in Malaysia

Feeding studies with our mosquitoes in the laboratory have complemented our field work in Malaysia

Traceability of Oxitec’s insects

In today’s society new product-developing companies need to recognise that efficacy alone is not sufficient. Environmental impact is key. In the case of products that are released in outdoor environments this is especially important. Frequent questions, regardless of the type of product, will be: ”where does the product go?”, ”How long does it persist?”, and ”What environmental impact does it have apart from its intended use?” But perhaps one question applies to all of the above: ”how do we know?”

Oxitec’s answer to this question has been to ensure that all its insects carry a gene that results in the insects producing fluorescent light when viewed under special filters. This helps us to distinguish a modified strain from an unmodified insect, which show no fluorescent light. More importantly, it provides an easily viewed tag that allows us to identify our insects in the field. We deploy traps that attract a fraction of the resident insects, and by screening the captured insects we can get an accurate picture of how many there are relative to their non-fluorescing wild counterparts. Recording and analysing data from traps placed over certain areas and time periods helps us to understand how far our released insects travel and how long they live.

These properties offer unique traceability of our insects, which is unique for most pest control products. Insecticides are sprayed but only chemical analysis using specialised equipment will provide information on how long they reside on a crop or how far they travel after spraying. Similarly, predatory bugs released for biological control of pest insects are rarely marked, so evidence of their success or environmental fate can be difficult or time-consuming to uncover.

The sterile insect technique (SIT), in which radiation-sterilised insects are mass-released for pest control, requires a method of marking for the same reasons as Oxitec’s approach, but the methods – such as dusting with fluorescent powders or feeding coloured dyes – can be unreliable.  To help address this limitation, the US Department of Agriculture is conducting on-going field tests of a genetically modified strain of cotton pest pink bollworm, which was developed with Oxitec, as the fluorescent protein marker could offer significantly greater reliability than the red dye used in the current SIT programme.  Field trap experiments show that the fluorescent marker is easily screened, and is backed up by molecular methods of detecting the Oxitec gene to offer two levels of detection.

This traceability means that we can trace our insects’ movements after release into the field, and in response adjust release numbers or location to optimise efficacy of pest management. Oxitec’s insects are self-limiting in the wild (they cannot breed), which – in combination with traceability – offers a degree of control that other pest management tools struggle to  provide.

 

Oxitec’s insects carry an in-built fluorescent marker that is visible under special filters.

Oxitec’s insects carry an in-built fluorescent marker that is visible under special filters.

 

Integrating solutions for Malaria prevention

Malaria causes the most human fatalities – 660,000 in 2010, according to the World Health Organisation – of any insect-borne pathogen. It is caused by infection with the Plasmodium parasite, transmitted by blood-feeding Anopheles mosquitoes in most tropical regions. Even when infection does not result in death, the febrile illness is debilitating, resulting in widespread suffering, significant economic loss and healthcare costs, especially in Africa. There are five species of Plasmodium that infect humans, with P. falciparum and P. vivax the most dangerous forms. Drugs against the parasite are available, but are unavailable or too expensive for many at-risk people, and the parasite rapidly develops resistance. Due to the ability of the parasite to mutate quickly, vaccine development has been challenging, but promising results announced this year by the pharmaceutical company GlaxoSmithKline indicate that a vaccine may soon be available that offers partial protection against malaria. The most effective malaria prevention strategies have focused on the prevention of human-mosquito contact. Especially in Africa, insecticide-impregnated bednets have been widely and successfully employed, although there is some suggestion that mosquitoes are changing their behaviour in areas of heavy use to feed at different times, avoiding the pesticides. Additionally, there is broad resistance to many of the pesticides currently in use, reducing their effectiveness.

Unfortunately, unlike dengue virus, which has a single primary and one secondary vector, there are many vectors of Plasmodium parasites. Globally, 41 species are considered dominant vector species (DVS), meaning that they are important and efficient vectors of human malarial disease. In many areas, multiple overlapping vector populations are responsible for disease transmission. The accompanying map shows the current estimated range for several of the DVS in Asia – a complicated picture! Recent work to map all the DVS across the global range of Anopheles mosquitoes has produced similarly complex maps for the Americas and Africa.

Beyond the number of mosquito species participating in the disease cycle is the range of behaviours and ecological niches they occupy. While most are heavily nocturnal, some also bite at dawn and dusk. Their preferred larval habitats range from lagoons to hoof prints and from marshes and bogs to fishponds and wells. Many prefer to bite animals, although all bite humans at some frequency; some are even human-adapted enough to prefer resting inside human habitations. Depending on the behaviour of malaria vector species present, pest management strategies may only effectively target a subset of the vectors participating in the disease cycle in a given area.

The picture is complex, with multiple problem mosquito species, but is there scope for more effective malaria control through the use of several partially effective preventative measures. To some degree this is already happening: the WHO estimates that better prevention and control measures have reduced global malaria fatalities by 25%. Could the addition of a new partially effective vaccine and other technologies bring infections down even further?

Oxitec’s genetic solution offers one potential tool. Its specificity to just the target species means it is very environmentally friendly, but it also means that it might best be employed against a small number of dominant vector species that persist despite other control measures. In India, for example, Anopheles stephensi is a significant vector of malaria and makes an attractive target for Oxitec’s genetic technology. To this end, we have worked with collaborators in the University of California to generate a modified An. stephensi strain that could provide just such a species-specific mosquito control tool (published this year in Malaria Journal, see accompanying newsletter article). If control of An. stephensi alone could be achieved, this could halt the spread of malaria in the large urban areas currently under threat.

Map from the Malaria Atlas Project. Hay, S.I., and Snow, R.W. (2006). PLoS Medicine 3: 12.

Map from the Malaria Atlas Project. Hay, S.I., and Snow, R.W. (2006). PLoS Medicine 3: 12.

In the news

Oxitec's Hadyn Parry on tackling dengue fever with genetically-modified mosquitoes | Wired 2013 video

Oxitec’s Hadyn Parry on tackling dengue fever with genetically-modified mosquitoes | Wired 2013 video

As Oxitec expands to work in new areas, impacting on a greater number of people, our work has been recognised through increased press coverage. This newsletter issue follows a spate of press coverage in the both international and national news, covering both our proposed olive fly trials in Spain and our dengue vector work throughout Brazil.

Oxitec’s olive fly trial proposal in Spain has generated considerable press coverage in both the UK as well as the rest of Europe.  This novel solution to controlling the olive fly pest has generated much interest within the olive fly industry but more recently, it has sparked coverage by the BBC.

On 20th November the BBC article with videos on “ How to rear genetically modified flies” and “GM flies tested ‘one step at a time’” followed a BBC Radio 4 interview the previous evening with Dr Martha Koukidou, who heads up our fruit fly team (http://www.bbc.co.uk/news/science-environment-24958489) and Dr Luke Alphey, Oxitec’s Chief Scientific Officer (http://www.bbc.co.uk/news/science-environment-24994433). The interest generated by this press package resulted in many spin-out articles throughout Europe. To support our regulatory work, we are carrying out predator and parasitoid studies requested by the Spanish regulatory authorities with wolf spiders and a laboratory strain of an insect parasitoid, Psytallia concolor, the larvae of which act as a deadly parasite to pupae of other insects.

Making sure people hear about our work is essential for Oxitec. We aim to reach as many people as possible with regular press updates on our Facebook and Twitter, however outreach for any small company can be challenging which makes a press article in Britain’s leading news agency a great achievement for Oxitec’s olive fly trial.

Another highlight of this quarter was the Wired presentation by Hadyn Parry, Oxitec’s CEO http://www.wired.co.uk/news/archive/2013-10/18/oxitec. Discussing the merits and challenges of tackling the vector borne disease dengue fever, Hadyn’s presentation focussed on how the use of Oxitec’s genetically modified Aedes aegypti mosquito has led to substantial drops in this mosquito’s population throughout release sites in Brazil.

Dengue is an international problem and reports on how our solution could be used were also published in Australia in November; while this is a cautious review of the technology focusing on the environment (http://www.ozy.com/fast-forward/crowd-control/3791.article), trials have indicated promising results with limited unintended impact.

Articles reviewing how the control of the dengue vector will affect people living around the release site are not often published, however the Los Angeles Times article “Dengue, where is thy sting?” (http://articles.latimes.com/2012/nov/01/world/la-fg-brazil-mutant-mosquitoes-20121102) provides a local perspective on the trials and how they can impact on dengue transmission. This article provided a voice to those we aim to help and reflects the warm welcome our control receives at release sites across Brazil.

Recognition by the BBC as well as Wired, a website dedicated to novel innovated inspiring news, is a testament to the creative success of the Oxitec solution. Our pest control solution receives international commendations due to its novelty but mostly due to the fact that results prove it to be extremely effective.