1. Delivering and developing oral contraceptives for grey squirrels
G. Massei, J. Lane, S. Beatham, R. Pinkham, K. Rickell, M. Gomm
National Wildlife Management Centre APHA
Royal Forestry Society meeting, National Memorial Arboretum
30 October 2018

2. Human-wildlife conflicts are increasing
Damage to crops, forestry, property
Disease transmission
Impact on native species
Road traffic accidents
Livestock predation
Worldwide human-wildlife conflicts are increasing. Traditional methods to manage these conflicts include shooting and poisoning. However, non-lethlal methods to manage overabundant populations of wildlife are increasingly advocated by the public.

3. Grey vs. red squirrel
Grey squirrels are currently at around 2.5 million, red squirrel numbers have reduced from approximately 3 million to 300,000.

4. Impact of grey squirrels
Reduce grey squirrel number to decrease impact on forestry
Impact of grey squirrels
Conservation of native species
Impact on forestry through bark stripping (£10 million per year)
affects tree growth and timber value
may cause death of tree, hence costs of restocking
increases the susceptibility of trees to various pathogens
36 species of UK trees are damaged by grey squirrels: beech, sycamore, oak, ash, maple, sweet chestnut, etc.
Reduce grey squirrel number to decrease impact on forestry
Grey squirrels are currently at around 2.5 million, red squirrel numbers have reduced from approximately 3 million to 300,000.
Control for 12 yrs in a beech woodland decrease % of squirrel damage from 50% to 8% of trees

5. Public attitudes Acceptability of grey squirrel control (n=3758)
Planting trees
Contraception
Kill traps
Shooting
Live capture (+ kill)
Biol. control (pine marten)
Warfarin poisoning
Acceptability of grey squirrel control (n=3758)
Blue + Red: very acceptable or acceptable
0% 20% 40% 60% 80% 100%

6. we need an oral contraceptive
Novel immuno-contraceptives
Vaccines inducing antibodies against proteins or hormones essential for reproduction
GonaCon
Gonadotrophin Releasing Hormone vaccine
“single-dose” injectable vaccines from our US partners
75-100% animals infertile for 2-8 years
Credible practical applications
BUT animals must be captured
In the last 15 years, novel single-dose immunocontraceptive vaccines have been developed that offer practical applications to manage wildlife. To deliver these injectable contraceptives, animals must be captured first, with significant cost in staff time. The availability of oral contraceptives would reduce staff time as these contraceptives could be delivered with relatively less effort to more animals.
we need an oral contraceptive

7. Fertility control applications via injectable contraceptives
Wild boar: 1 dose GonaCon stopped reproduction in 92% sows for 5-8 years
Feral goats: 1 dose GonaCon reduced fertility by 83-92% for > 4 years
California ground squirrels: 1 dose GonaCon reduced the reproduction by 91% (year 1) and 96% (year 2)
Examples of successful applications of the immunocontraceptive GonaCon to wildlife. The contraceptive was delivered via a single injection. These studies showed that GonaCon is very effective and may cause infertiility for many years.

8. Novel formulation to increase effect of oral vaccine
Oral immuno-contraceptive vaccine targeting GnRH
Biology, behaviour, population dynamics
APHA & collaborators developed a novel GnRH-based oral vaccine
60% rats fed the contraceptive did not breed
(control rats: 10-30%)
Contraceptive fed in a bait : reduced response to the vaccine
Novel formulation to increase effect of oral vaccine
The project is based on a previous study, carried out by our group and collaborators, where we developed an oral contraceptive that made 60% laboratory rats infertile. When the same contraceptive was delivered through a bait, the effectiveness was reduced. Hence we are working on a novel formulation of this vaccine.

9. Novel formulation to deliver an oral contraceptives
Spores and pollen grains
Pollen/spores: natural, renewable, commercially available
Genetic material removed to obtain sporopollenin exine
capsules (SPECs)
Proven effective delivery of drugs such as fats,
oils, vitamins, enzymes, hormones, ibuprofen
We formed a partnership with a UK company that patented spores and pollen grains (referred to as “SPECs”) to encaspulate and deliver a wide range of drugs. When SPECs are fed to animals (or human volunteers), the passage rate of SPEC-encapsulated drugs through the alimentary canal is slower than that of non-encapsulated drugs, possibly due to the “spiky” morphology of the SPECs. As a result, drugs are delivered more gradually and their effects seem to last longer.

10. SpECs for an oral contraceptive vaccine
Proven vaccine delivery in SPECs fed to mice
increased antibodies in mice
antibody response lasted for up to 7 months
a possible mechanism for oral vaccination

11. Developing and delivering oral contraceptives to control populations of grey squirrels
Identify SPECs species
Lab trials with rats to test SPEC-encapsulated oral vaccine
Monitor bait uptake by squirrels (lab + field)
Lab trials with grey squirrels
Optimise bait uptake by squirrels
Field pilot trials with squirrels to confirm efficacy
Large-scale trials to monitor effects at population level
Initiate trials for registration package
Year Year Year Year 5
S9 The project, which started in April 2017, will progress from laboratory trials with rats (to test various formulations of SPEC-delivered contraceptives) to captivity trials with squirrels and eventually field trials to test the effectiveness of oral contraceptives on local populations of grey squirrels. In parallel, we are developing 1. methods to monitor patterns of bait uptake by free-living squirrels, to maximise ingestion of baits containing the contraceptive and 2. methods to deliver the baits to grey squirrels only.

12. The project team Project leader Field studies coordinator
1 statistician
Field studies coordinator
Lab studies coordinator
2 lab technicians
2 modellers
4 field ecologists
2 lab ecologists
Two teams in USA and France
The Animal & Plant Health team comprises 14 staff in addition to collaborators in the UK, France and the US, the latter in charge of assembling the vaccine.

13. Year 1 results: testing oral vaccine in model species
Tested SPECs of sunflower and club moss fed to rats
60% (n=12 of 20) had antibodies to oral vaccine
but not sufficient to cause infertility
100% rats (n= 19) had antibodies to the injected vaccine
with 95% sufficient to cause infertility
We are testing a modified version of the squirrel-specific hoppers previously used to deliver warfarin. We have used Rhodamine B (RB) as a bait marker: RB appears as fluorescent bands in hair and whiskers of squirrels that ingested a bait. This marked can be used to quantify the proportion of a population exposed to oral contraceptives.
More work in Year 2 on formulation of oral vaccine

14. Year 1 results: delivering contraceptives to grey squirrels
Developed grey squirrel-specific hopper to:
deliver baits that will contain oral contraceptives
monitor patterns of bait uptake by individual squirrels
Tested Rhodamine B (RB) to:
monitor bait uptake in the population
Pilot trial
51 grey squirrels trapped in 2 woods, PIT-tagged, released
48 bait hoppers with PIT-tag readers deployed
We are testing a modified version of the squirrel-specific hoppers previously used to deliver warfarin. We have used Rhodamine B (RB) as a bait marker: RB appears as fluorescent bands in hair and whiskers of squirrels that ingested a bait. This marked can be used to quantify the proportion of a population exposed to oral contraceptives.

15. Year 1 results: delivering contraceptives to grey squirrels
Bait hoppers
Established how often squirrels visit hoppers
> 93% PIT-tagged squirrels entered >1 hopper at least once in 4 days
Rhodamine B
After 4 days of RB-treated baits > 56% squirrels had RB bands in hairs
We are testing a modified version of the squirrel-specific hoppers previously used to deliver warfarin. We have used Rhodamine B (RB) as a bait marker: RB appears as fluorescent bands in hair and whiskers of squirrels that ingested a bait. This marked can be used to quantify the proportion of a population exposed to oral contraceptives.

16. Year 1 results integrated with Defra study
Model the effort required to eradicate grey squirrels via culling, contraception or culling + contraception
We have developed a mathematical model to assess the impact of different methods of population control on squirrel numbers.

17. Year 1 results integrated with Defra study
The results of the model suggest that culling, carried out using a minimum of 3-4 traps per hectare, can reduce drastically a local population of grey squirrels in a few years. However, this method has significant costs associated with staff effort as traps, that can be activated for several months, must be checked every day.
Culling with different levels of effort

18. Year 1 results integrated with Defra study
The model also suggested that integrated management, where culling is initially used to decrease the size of the population and is followed by the use of oral contraceptives, might be the most cost-effective method to reduce numbers of squirrels
Culling in Year 1, followed by fertility control with different levels of efficacy

19. Highlights of Year 1
A method, based on SPECs, to encapsulate an oral vaccine
Induced an immune response to an oral contraceptive vaccine
A food hopper to monitor bait uptake patterns by individuals
A bait marker (RB) to quantify the % of grey squirrels feeding on baits that will contain oral contraceptives
Established captive colony of grey squirrels to test contraceptives
We have developed a mathematical model to assess the impact of different methods of population control on squirrel numbers.

20. Scalable applications for oral contraceptives
Oral contraceptives scalable to new species and contexts
Non-native invasive species, incl. feral animals
Over-abundant wildlife
Where culling is illegal, unfeasible, undesirable
To complement culling to control populations or their economic / environmental impact
As public demand for non-lethal methods to manage human-wildlife conflicts increases, oral contraceptives could be applied to many species and contexts or used to complement other methods of population control

21. Non-lethal control : when?
When lethal control is:
illegal
unacceptable
unfeasible
unsustainable
environmentally hazardous
ineffective
BUT also complementary to lethal control

22. What next… Integrated Pest Management
We have had spring traps for many years but we did not solve the problem
Integrated Pest Management
Sustained control over long period
Less staff intensive
More publicly acceptable
Fertility control

23. …the squirrel team! Questions? With thanks to…