Badger culling in the U.K. – step one: cull badgers, step two: …?, step three: profit!

Image from BBC News

A friend of mine thought this would interest me when I last visited him, and I had him send me the links discussing badger culling in the UK to control the spread of bovine tuberculosis (Mycobacterium bovis).  In addition to having an economic impact,  bovine TB also carries a zoonotic concern. I thought I would learn more about the issue, and see what the literature says about the success of the program.

Badger culling has been a part of TB control in the United Kingdom since 1973. Despite this and other programs in place, incidence of TB has only increased during that time. In the thousands of biological and environmental risk factors that have been associated with TB infection risk, Badgers have been identified as an important reservoir and potential vectors for the disease.

The politics surrounding the issue are interesting, and provides a great case example of how public perception can be skewed for certain species. The regular players are all there: the economically invested (in this case, cattle farmers and associated industries), the scientific community, outspoken animal interest groups, a generalized public perception, and the federal government trying to cater to the majority of voters (or campaign contributors, depending on the official and your own opinion). Lets break down these players.

The Economically Invested

On this issue, everyone seems to be on board that bovine TB is a problem in the UK. The ones who really care though are cattle producers, meat and dairy processing companies, and the retail ends associated with those products. When oppositional parties want to discredit this group, we see them described as “big corporations” only concerned about the bottom line. These claims are many times true, as even the small farmer has to maintain a decent profit margin to provide for him or herself. This group tends to be less publicly oppositional, preferring to exercise their strength through advertizing, lobbying, and funding research that can help support their position. Within this issue, I wasn’t able to find any ads produced by organizations in the UK, however, I did find some farmer concerns over the issue. One was the difficulty in getting approved for a badger cull in your area, and the other was the fear of response from activist groups if they did choose to participate in the program. The position of the farm interest groups is that the spread of bovine TB is an animal welfare and economic concern, and that badger culling will be critical in suppression of the disease. Local wildlife can often aid transmission of disease; however, we have also seen blame placed incorrectly on wildlife in other situations.

Animal Interest Groups

There are many groups in the UK that advocate for Animal interests, and they’re pretty much unanimous in the opinion that culling badgers is not an effective or ethical way to combat bovine TB prevalence. However, they do have different techniques in approaching opposition. While many of them strictly condemn the practice and advertize to sway public opinion, one group (with the support of many others), Gloucestershire Wildlife Trust, has been independently vaccinating wild badgers for bovine TB. At this time they haven’t investigated the effectiveness of the vaccine itself, but rather the economical viability of the process. Their results so far have shown that it would cost more than twice as much to vaccinate an entire hectare instead of culling. Typically these same groups in other controversial situations are very politically active.

The General Public

Generally the least informed and (arguably) the most powerful, the majority of public opinion represents the majority of voters and consumers. Regarding badger culling however, most of the general public has been shown in polls to oppose the practice. Agricultural controversies are often represented by government and industry actions that don’t necessarily mirror consumer or public preference, but instead are economically viable. Whether it’s often advocated for or not, above all else the majority of the public wants inexpensive food, and that benefit often outweighs other consumer preferences (though not always). An interesting examination of the public perception of badgers is discussed within this controversy, and this argument can also apply to other similar situations we have seen over the years. BBC explored the role of badgers in popular children’s stories, and related them to other species that receive special protection even if they are not endangered. An example from the states would be our attachment to wild horses as an icon of America, and some of the debates we’ve seen surrounding not only control of wild horses, but within discussions on using horses for food. Kevin Pierce from the article sums this feeling up well:

“It’s an image issue. A lot of farmers like badgers but we also want to control the disease. If your vector spreading TB was a rat, I’m sure that there’d be no problem for farmers in securing a license to take action.”

The Government

Tasked with the burden of trying to please everyone, the federal government often responds to the loudest collective voice along with their own advisers, analysts, and ethics. In this case, we do know that the government has moved forward with culling as they have in the past. Evaluating the motivation behind these decisions is an endless discussion, whether it’s a working system or corrupt is beyond the scope of this post. Feel free to express your opinions on the process in the comments below. The best I hope for is that while looking out for my interests, my officials attempt to remain objective, and speaking of objectivity…

The Scientific Community

I’ve left us for last. The example of objectivity and a lens of evidence to weigh a cost-benefit analysis of the issue not directed by personal interests, concepts of morality, or hidden goals. Or so we would hope. As a realistic scientist who has read a lot of peer-reviewed research, I know that we are never truly objective. All funding comes from somewhere, we interpret our own results, and while we try as hard as we can to be objective, there is no perfect experimental design immune to bias. However, as creator of this site, I obviously hold research in high esteem, so lets look at some of the literature regarding the effectiveness of badger culling in curbing the spread of bovine TB.

According to the sources I found, it appears that badger culling does have a positive effect on the rates of bovine tuberculosis, but strictly within the areas the culling occurs. There’s a beneficial cumulative effect after several years of a culling program (in the reduction of detrimental effects in surrounding areas), but it isn’t necessarily lasting, cost-effective, or repeatable in different situations. The consensus amongst several studies is that localized culling actually increases TB rates in the surrounding areas, due to the displacement of normally local badger populations, and additional factors that we don’t fully understand. Given these effects, there seems to be a general consensus in the literature I viewed that at best badger culling is not a cost effective way to reduce TB transmission, and at worst contributes to the spread of disease.

Culling programs always have fierce opposition from many sources, whether it be culling sea lions to protect Columbia river salmon, culling grey wolves to protect livestock, or culling tame geese that are causing damage to city parks. There are serious concerns from conservationists and animal activists about the effectiveness of such programs that can be well founded, and the controversy surrounding badger culling in the United Kingdom is a clear example  of why these decisions would be more effective if they are backed by empirical research and economic analysis before being presented as a moral dilemma.

ResearchBlogging.org
Donnelly CA, Woodroffe R, Cox DR, Bourne J, Gettinby G, Le Fevre AM, McInerney JP, & Morrison WI (2003). Impact of localized badger culling on tuberculosis incidence in British cattle. Nature, 426 (6968), 834-7 PMID: 14634671
Donnelly CA, Wei G, Johnston WT, Cox DR, Woodroffe R, Bourne FJ, Cheeseman CL, Clifton-Hadley RS, Gettinby G, Gilks P, Jenkins HE, Le Fevre AM, McInerney JP, & Morrison WI (2007). Impacts of widespread badger culling on cattle tuberculosis: concluding analyses from a large-scale field trial. International journal of infectious diseases : IJID : official publication of the International Society for Infectious Diseases, 11 (4), 300-8 PMID: 17566777
Donnelly CA, Woodroffe R, Cox DR, Bourne FJ, Cheeseman CL, Clifton-Hadley RS, Wei G, Gettinby G, Gilks P, Jenkins H, Johnston WT, Le Fevre AM, McInerney JP, & Morrison WI (2006). Positive and negative effects of widespread badger culling on tuberculosis in cattle. Nature, 439 (7078), 843-6 PMID: 16357869

Article Review: Vaccine Reactions

I’m apparently still on this immunology kick, because I seem to be finding it everywhere. Heck, I recently learned that we’ve cured the allergic response to peanuts and eggs in lab mice. Check out the link, the author is hilarious and the material is interesting.

These two articles offer a great look at the overall prevalence and risk factors associated with vaccine-associated adverse events. The components within the vaccine that cause these events are the antigen itself, adjuvants, preservatives, stabilizers, and residues from the tissue culture used to grow the vaccine (Moore, 2005). Vaccine reactions are similar to any acute allergic reaction, and can present with a variety of mild to severe symptoms. The mild being lethargy, anorexia, fever, edema (generalized or local to the injection site), pruitis, uticaria (hives or wheals), and pain at the injection site; the severe being vomiting, dyspnea (labored or shortness of breath), and anaphylaxis. There’s a lot of information about when certain symptoms tended to occur at intervals after the vaccines were given, but any reaction that isn’t within the first 3 days is pretty much never going to be life threatening. If anaphylaxis is going to occur, it’s going to be immediately following vaccination.

The really useful information was the breakdown of risk factors that can be used for client communication. I’ve decided to discuss them here, broken down into cat and dog categories.

Image from meow-cats.com

First, let’s start with cats. I almost like these numbers more because you don’t have to take into account bias based on animal or breed size, as most cats fall into the <20 lbs category. Nonetheless you still have to remember that a 4 pound kitten does way only a fraction of that 5 year old chubby (BCS >5 on a 9 point scale) longhair it will grow to be.

So the first two risk factors require a little bit of thinking in context to explain the numbers. It seems that cats weighing 2-4 Kg (4.4-8.8 lbs) and approximately one year of age are most at risk compared to other weights and ages. The high numbers for these groups can be explained by the number of first encounter events that occur. If you’re recording vaccine reactions, you will record less in older age groups and higher weights (low weight under 10 lbs is going to be suggestive of a young age rather than a smaller cat), because if an adverse event occurred at a young age, either the animal is no longer vaccinated or steps are taken to reduce its risk (medication, strict scheduling, vaccine selection). That being said, just because the numbers are higher by circumstance, this information is very relevant in a clinical setting. Knowing the epidemiology of these events can help technicians at clinics determine when the discussion of vaccine reactions is “routine” or “protocol”, or when it really needs to be a time to educate the client. Vaccine reactions may need to be just a bullet point when Schrodinger is there for his 4th rabies booster and a discussion when he’s receiving his kitten series.

Sex and neuter status have a large impact on reaction risk as well. Intact males actually have a lower risk of adverse events than neutered males and spayed and intact females. Apparently, estrogen has an immune boosting effect, while testosterone has an immune suppressing effect. This benefits intact males when it comes to all allergic reactions (and possibly auto-immune disorders).

Here’s the big one, and the one clinics have the most control over. With each additional vaccine given in a single visit, the risk of an adverse event increases by 28% in cats. That’s huge. Any cases of severe anaphylaxis or death recorded in the study were preceded by the animals receiving 3 or more vaccines in one visit. So clearly the biggest thing any clinic can do to prevent adverse events (or at least severe ones) is to adopt a vaccination schedule that prevents multiple vaccinations from occurring within the same visit. This can be difficult as clients will not want to end up paying for multiple exams throughout the year, but with boosters outside of rabies, exams shouldn’t be necessary unless an annual or other scheduled exam is due. As far as specific vaccines being more prone to adverse events, the only suggestive evidence was when both FVRCP and FeLV were given within the same visit. This is explained by both having two concurrent vaccinations given, and also the theory that vaccines containing multiple antigens or covering multiple serovars (multivalent) are more likely to illicit reactions. Interestingly, while clients are often scared by the potential for vaccine caused neoplasia from the rabies vaccine, it was among the lowest reaction rates observed with the administration of a single vaccine.

Image from peteducation.com

Dogs had much more biased data within the age and breed groups because there is an obvious relationship between body mass and the potential for reaction. When looking at the dog population, a chihuahua can be as little as 6% of the weight of a bullmastiff, yet they receive the same 1ml dose of vaccine. This means that an 8 lb Chihuahua is going to receive proportionally 15 times more vaccine than a 120 lb bullmastiff. Not surprisingly, this causes a bit of inflation in the number of reactions in groups that are smaller in size, such as toy breeds and puppies. The highest risk group in size was 0-10Kg (0-22lbs) and the highest risk age was approximately 2 years of age (with higher rates for <2 than the rates of >2).

Just like I mentioned before when talking about cats, the greatest risk factor for reactions in dogs was the amount of vaccines given in one visit. The difference though, is how the large weight distribution in dogs makes this even more important. Small dogs (<10Kg) are similar to cats in that their risk increases by 24% with every additional vaccine administered that visit, while large  dogs (10-45Kg) increase their risk by 12 percent. All 3 dogs in the study that suffered fatal reactions received 4 or more vaccines at once.

Breed dispositions were difficult to pinpoint, as the suspected breeds are all small breeds which suffer a higher rate of reaction already due to their size. There is suspicion that dachshunds may be predisposed to allergic reactions in general, but so far the evidence is inconclusive concerning vaccines. Only the Lyme vaccine appeared to carry a higher risk than any other, showing again that, with the exception of neoplasia concerns, rabies does not carry with it any additional risk. Spayed and neutered animals, as in cats, are more susceptible to reactions; however the difference between intact and spayed females is much larger in dogs than in cats (where they are nearly identical). Dogs do seem to display an interesting trend where vaccine reactions are more likely to occur on the 3rd booster in a series, likely catching clinicians and clients off guard as they have received the first two without incident. This just states again that the puppy and kitten periods (and new patients) are of much more relevance when discussing vaccine reactions with clients.

The articles are both great, and contain an excellent statistical analysis of millions of animals. They provide a great overall picture of the epidemiology of vaccine-associated adverse events, and are definitely worth a read for both veterinary doctors and staff. Knowing a couple of the more important statistics can reassure the client and lend credibility to technicians that are responsible for discussing these issues.

ResearchBlogging.orgMoore, G., DeSantis-Kerr, A., Guptill, L., Glickman, N., Lewis, H., & Glickman, L. (2007). Adverse events after vaccine administration in cats: 2,560 cases (2002–2005) Journal of the American Veterinary Medical Association, 231 (1), 94-100 DOI: 10.2460/javma.231.1.94

Moore GE, Guptill LF, Ward MP, Glickman NW, Faunt KK, Lewis HB, & Glickman LT (2005). Adverse events diagnosed within three days of vaccine administration in dogs. Journal of the American Veterinary Medical Association, 227 (7), 1102-8 PMID: 16220670

Newsworthy: Vaccine linked to “bleeding calf syndrome”

When I first started working in an actual clinic, I was blown away with the education I received in vaccine administration. Before at the shelter my instruction included solely how to administer them and not to be bitten while doing so. Spending a minute to educate clients on vaccine reactions, the steps we took to prevent them from happening, and the importance of the proper scheduling of a series were all new to me, and considering how seriously we took all these things, it vastly contrasted with my training at the shelter. How vaccines work has always been interesting to me, and the immunology involved isn’t terribly complicated on the surface. Even if the mechanisms escape me, I can still visualize the flowchart (something I wish I could consistently do with G-proteins, a crucial topic but one I constantly have to review).

Image from Veterinary Laboratories Agency

Anyway, the point is I was really interested in this article. Bleeding calf syndrome is technically called bovine neonatal pancytopenia (BNP), but is probably still a frightening thing to see. It actually only emerged in 2007. The characteristic bleeding is caused by thrombocytopenia after the calf’s bone marrow becomes compromised. The lack of platelets causes the appearance of bleeding through the skin the name refers to. A group of doctors in Germany were able to determine the etiology of the condition (which has a calf mortality rate of 90%). Based on another study, they knew that the colostrum given to affected calves could also induce the symptoms in other unrelated calves, and after not finding evidence from pathogenic or genetic causes looked at an “immune mediated process” (Deutskens, 2011).

What they found was that there was a correlation between cows vaccinated for Bovine Viral Diarrhea Virus (BVDV) and calves suffering from BNP. After a lot of spectroscopy and protein identification, they found that the vaccine actually was the cause. What the issue was, is that the BVDV vaccine is made using kidney cells from cows, instead of another species (for example many human vaccines are cultured in pig cells). Here’s how that works: there is a specific protein “map” coating all nucleated cells that the immune system uses to identify which team they play for. Anything with a different protein coat is assumed to be foreign, and is attacked. This is the major reason why donated organs are rejected, because the donor has a slightly different “map” than you and your immune system assumes it’s trying to hurt you. With the vaccine grown in bovine cells, remnants or copies of this Major Histocompatability Complex (MHC, the “map”) are introduced to the mother, who has an immune response to them.

This is where it gets interesting, the antibodies the mother makes to attack this are called alloantibodies, and they don’t hurt the mother. They just become another antibody she reserves along with the ones that attacked the rest of the BVDV vaccine. None of her cells have that foreign “map”, so none of her cells need to worry about that extra antibody she created. However, the alloantibody gets stowed away in the colostrum along with all the others just before partuition, still ready to attack the MHC the vaccine was made with. If by coincidence the MHC of the calf is the same as the one in the vaccine cultures, then those alloantibodies given to the calf through the dam’s colostrum will attack cells within the calf, starting with blood cells and moving to the bone marrow. Making it technically not an auto-immune response, because it comes from a foreign immune system, but still a case of friendly fire. Those alloantibodies in the colostrum treat every calf cell featuring that MHC as if it’s an infection.

It should be noted that other vaccines for BVDV that are grown using non-bovine cultures do not cause these problems. This is because if the mother creates antibodies for the MHC of another species, there is no way that the calf can be affected by them. The authors of both the news article and the journal article mention that this serves as an example why same-species vaccine cultures and formation of alloantibodies should be avoided.

Check out the journal article for yourself, the introduction and discussion are well written and interesting. There’s also a similar alloantibody caused disease in humans called Neonatal Alloimmune Thrombocytopenia that’s interesting, the major difference being that the alloantibodies are introduced through the placenta instead of ingested through colostrum.

ResearchBlogging.orgDeutskens F, Lamp B, Riedel CM, Wentz E, Lochnit G, Doll K, Thiel HJ, & Rumenapf T (2011). Vaccine-induced antibodies linked to Bovine Neonatal Pancytopenia (BNP) recognize cattle Major Histocompatibility Complex class I (MHC I). Veterinary research, 42 (1) PMID: 21878124

Article Review: Leptospira and Leptospirosis

In my latest ScienceDirect purge, I came across this article covering Leptospirosis. I had no idea it would be such a dense read, figuring it would be a simple review of the disease with emphasis on new discoveries. I ended up using a lot of immunology references and Google searches. This article isn’t just an entry from the Merck manual.

The article does a very good job of covering Lepto microbiology, but I was especially impressed with the point they made to identify everything we don’t know. Indeed that was the emphasis of the article, that lepto contains so many pathways unique to it as a bacterium that we don’t know nearly as much about it as we do something like E. Coli. Additionally, Lepto is extremely hard to culture, as you end up with non-virulent colonies. They identify and isolate the virulent daughters by inoculating lab animals.

You might assume that immunity to Lepto is a simple thing, given how prevalent Lepto vaccination is due to the zoonotic risk. However the article makes the point multiple times that immunity to one Lepto serovar does not grant immunity to others, though occasionally it can help grant passive immunity or resistance across different species. While the exchange of genetic material between parent and daughter lepto colonies is not well understood, it appears to be slow mutating, which is interesting given how unique the antigens between serovars seem to be.

There’s a lot of complicated immunology discussed in the article that I don’t feel qualified to comment on, but it’s very interesting, and I recommend glancing through. The more microbiology I learn the more I understand that 99% of the workings of the cell happen on membranes (a statement that probably produces a loud “duh” from any student, biologist, or doctor). For a more clinical discussion of Lepto, a simpler reference like Merck or Blackwells will help, as well as several peer-reviewed sources that the article itself recommends for information on clinical presentations.

Adler, B., & de la Peña Moctezuma, A. (2010). Leptospira and leptospirosis Veterinary Microbiology, 140 (3-4), 287-296 DOI: 10.1016/j.vetmic.2009.03.012