As many of you now know, a rash of sudden illness and deaths hit our local alpaca community, as well as other regions of New England, this past fall (2005). Heartbreakingly, the most frequently affected were newborn crias, but also a previously healthy yearling died at a farm close to us.

At first it was a relief when the diagnosis of EEE (Eastern Equine Encephalitis) was confirmed at least we knew the name of the enemy. until we realized that we were all so vulnerable, there being so little we could do to protect our alpacas from this mosquito-borne illness. And there was no vaccine that had been tested in alpacas, like there was for horses. All we could do at the time was to reduce the mosquito population on our farms as much as possible and hope for an early frost.

This is when local breeders and vets, NEAOBA, and Dr. Bedenice at Tufts got together an expediently assembled research project funded by donations collected by NEAOBA and the Alpaca Research Foundation (ARF). Results from this study  Humoral (antibody) Response to EEE Vaccination in Healthy Alpacas 12/01/05-11/30/06 are now emerging. For more details of this work see the Autumn 2006 issue of Alpacas Magazine.

Testing our whole herd for EEE virus exposure during the NEAOBA-funded seroprevalence study revealed the surprising result that a significant proportion of the alpacas on our farm had been exposed to the EEE virus, though none got sick.

So in addition to adopting/continuing many of the sound herd management practices outlined by Barbie Tilton in her article (this issue), we at Sallies Fen felt that our particular on-farm risk was high enough to warrant us going for vaccination to try to protect our most vulnerable alpacas who are, of course, the crias.

It was tough call, because the only way to target the crias for protection (at least through a vaccination program) was to vaccinate the pregnant dams. That way the crias (in theory) would be able to benefit from passive transfer of the dams EEE antibodies in her colostrum.

Of course no pregnant females were included in the ARF/NEAOBA EEE Vaccine Trial mentioned above, so we were going out on a limb. We had several discussions with our vet, and with Dr Bedenice at Tufts, both of whom stressed that the EEE vaccine we would be using was a killed vaccine, so was really quite safe. Still, we were nervous, but we decided to start a course of vaccinations as soon as we could, followed by 2 boosters - given 4 weeks apart.

We did the first round of vaccinations of the pregnant females in early June and this went well. Top priority was the dams who were due to deliver crias in the fall, when there is much the greatest risk of mammal-biting EEE-carrying mosquitos. We used the Encevacw/Havlogen EEE (and WEE) vaccine, by Intervet. The vaccine can be found in the American Livestock supply catalog for horses (www.americanlivestock.com).

One piece of information that gave us a big confidence boost that we were doing the right thing came soon after the first round of vaccinations had been completed at our farm. One of our dams (Cassie), who we knew from the NEAOBA - funded seroprevalence study had a high natural titer, produced a cria (Brijit) who at 9-days old we were delighted to learn also had antibodies to EEE.

Though this evidence would not stand up in a court of law (because there is a tiny chance that EEE mosquitos were about early enough in the year to infect Brijit), we were thrilled to think that little Brijit most likely got her protection through Cassies colostrum so we concluded that it was at least possible for vaccinated females to pass their protection to their crias - yea!

We have also been vaccinating our yearling girls and crias, starting at a few weeks old. As far as I understand it (and I am NOT a vet!), even if the cria is protected by passive transfer from the dam, vaccination helps to stimulate their own adult immune response to provide protection after the maternal antibodies naturally clear from their system (at about 3 months old).

As an added precaution, we arranged to have plasma collected from a yearling female, Nefertiti (Nef). Nef stood out early among animals from the several farms involved in the seroprevalence study for her whoppingly high natural levels of EEE antibodies. She maintained these high levels thru June 2006.

Nefs appointment at Tufts for plasma collection happened to coincide with the horrid late July/early August heat wave that affected most of the US. Our trailer does NOT have A/C, but our Subaru Forester DOES so she got to ride in style or at least she stayed comfortable in a much cooler environment than the rest of her herd were dealing with!

We hope we dont need it to transfuse a cria sick with EEE, as that will be an emergency life/death situation, but we are ready just in case.

We would like to stress that this is anecdotal evidence only from the experience of our single farm, and we are not endorsing any particular course of treatment, but at the time of writing (end August 06) we have given the third and final booster to most of our girls and have vaccinated 4 crias. All are healthy. so far so good!

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