Veterinary Parasite

Throughout my career as a veterinary undergraduate, many of our exams have been in the Multiple Choice Question (MCQ) format, a method of assessment that, in my opinion, comes with considerable drawbacks. Generally, a question is asked, with 4 or 5 possible answers, of which one is correct. The first problem is one of testing depth of knowledge - with an MCQ, the correct answer is by definition already in front of the examinee, so simple questions of understanding are rarely asked, as they will be answered correctly by 99% of students. The questions asked are normally on very specific, and pretty detailed, pieces of knowledge. This contrasts to the challenges faced by a practicing vet - understanding a problem is absolutely vital, whereas exact facts and figures can always be looked up. As such, the MCQ is an inadequate method of assessing if the candidate has what is needed to achieve their ultimate aim, i.e. practicing as a veterinary surgeon.

The second problem is one of statistics. If candidates were to blindly guess at questions, they would, on average, answer one in four/five of these correctly, skewing the results of the exam. In order to combat this problem, many exams introduce “negative marking,” whereby 1/4 or 1/5 of a mark is deducted for every incorrect answer, with the stated aim of decreasing guessing. This is a totally ineffectual measure, as the student versed in statistics will realise that blindly guessing in the face of negative marking will yield neither a gain or loss of marks. So, if they have the slightest inkling of the answer, it is in their favour to go with it.

After having three (non-negatively-marked) MCQ exams last week, these thoughts have been buzzing round the old brain, and I’ve found a partial solution.  Tell the students that the examination is negatively marked - this achieves the aim of discouraging outright guessing, which could unfairly skew some students results upwards.  However, don’t actually apply negative marking - this allows students who were unfortunate enough to think they knew the answer, but were in fact wrong, to go unpunished, thus reducing the downward skew of results for unlucky students.  Of course, this would rely on utmost secrecy about the non-application of negative marking - something probably quite difficult to achieve within an organisation as insular as a vet school!

As a grand finale, I present to you an idea that will most likely see me beaten to a pulp by my classmates!  The best solution to the MCQ problem is, in my opinion, to use more traditional methods - short and long answer questions, with a choice of essays can test a wide range of subjects, to varying depths.  Importantly, it also tests understanding, rather than just parrot fashion learning.  It does of course require considerably greater effort to mark…which may or may not be a stumbling block to its reintroduction!

Ever since I first read about it several years ago, I wanted to have a go at clicker training. For the uninitiated, it is training using a device that makes a short sharp click. This noise is associated with a positive emotional state, often by association with food, and a click then used to let the dog know they have done something right. It’s very useful, mainly because of the ability to sharply define points of reward, for example, if I wanted to teach a dog to sit, then it may offer the behaviour (sitting down), but by time I’ve given it the reward, say a biscuit, it has stood up again. This leads to the unintentional rewarding of “standing up” behaviour, the polar opposite of our aim! With the clicker, we can give a click at the exact moment the dog’s backside hits the ground. We will still give a treat/reward to the dog, but the dog associates this with the click, not the behaviour being formed when it gets the reward.



Anyway, our first week of lectures after Christmas were on animal behaviour, and clicker training was brought back to the forefront of my mind. I was also lucky to see a demonstration from Sarah Heath, a veterinary behaviourist of exceptional standing. After seeing it done, I was chomping at the bit to have a go, so I had to acquire two tools:

1) A clicker - This was relatively easy to acquire - £1.50 from eBay!
2) A dog - This is Rosie, slightly harder to acquire, as not only did she live with my parents 200 miles away, but she also wasn’t massively enthusiastic. Fortunately, once she realised food was involved, she quickly came round to the scheme!

Anyway, to the training! I decided on a pretty simple target behaviour - sitting on a mat placed somewhere in the room. The first thing to do was associate click with good - so a click followed by a biscuit, until her ears pricked at the sound of the click, clearly expecting the reward! With this association in place, I moved on to getting her to sit. OK, this was pretty simple, given she’s been trained to sit already, and even without any prompting on my behalf, she quickly picked up that I wanted that backside on the floor. Now we wanted to transfer that sitting behaviour from anywhere to a specific place. She was pretty taken with the whole sitting thing at this point, so I got her to move around with moving myself, tempting her with treats, and things like that. Whenever she had paws on the mat, she got a click. Now, using a bit of body lingual suggestion, I got her to offer a sit on the mat, with a click when she hit the deck. It took a while, but I’m now the proud owner of a dog that will sit on a mat, and expect food for it! The next step is to associate sitting on the mat with the word “Mat”, and then we might have something half useful!

I wasn’t sure how long all this should be taking, but assuming it’s variable between dogs, and knowing my dog ain’t the sharpest knife in the drawer, getting this far in 2×20mins/day for 5 days isn’t bad! Even better, now I know I can get the dog to do whatever I like, it’s time to ingrain some parent annoying behaviours in her!

Ah, the question, the bane of every vet student’s life. The killer interview question that will “make or break your application!” The justification of your hopes, dreams and aspirations. To be summed up in an answer of approximately 1 minute, maximum. Without sounding like a hopeless romantic who wants to “save all the cuddly little animals.”

It’s a question I found myself asking myself a few times during the dark, pre-clinical days of the course, and here’s what I came up with.  I’d like to see some comments as well - why do you want to be a vet? Or if you don’t, why did you choose your career path?  Anyway, here goes…

For as long as I can remember animals have been a part of my life - cats, dogs, guinea pigs, rabbits and mice as family pets. Horses at the stables when we went riding. Cattle on my uncle’s farm. It’s unsurprising then that I began to develop an interest in animals, even at a very early age. As I then entered my teens, I found myself standing out in certain areas at school - Sciences and Maths to be exact, but it was always Biology that really caught my interest, well as long as you leave the plants out of it! It was a natural progression from there to start thinking about combining my natural abilities with my interest in animals, and it’s no shock that veterinary science came up somewhere along the line. This next part almost makes me vomit when I say it, but I have to admit I was influenced by TV programmes - Animal Hospital and Vet School were both in their prime right around the age I started to think about the future, and the image of the vet as a lifesaver, a real hero made an impact. Soon, it came round to work experience time, and I was lucky enough to get a place with a local vets. That was the real turning point, and I haven’t looked back since. Explaining how I got to this point is relatively easy, but why do I want to be a vet now? Well, it isn’t just the hero status! I’m an outdoorsy man, and the thought of having a life driving round the countryside is incredibly appealing. I considered being a rural postman, but there was too much bloody competition! The final, somewhat shallow reason lies with my massively competitive nature - I like to be the best, and to be the best means putting the biggest challenges in your way. Veterinary science was the biggest challenge I knew of, and remains the biggest I know of today.

Of course, this is a bit long winded, so I also have a single stock answer to this question - “Well, it’s the only way you can kill animals legally!” It’s a shame this blatantly isn’t true - there are plenty of other ways to kill animals legally!

Well, as this is a vet student’s blog, and also a self-proclaimed parasite’s blog, I thought it was about time to write something about veterinary parasites! I have a “special affinity” with parasites, after a year resitti…I mean studying them in more depth, and to my shame and horror found myself enjoying the subject. Anyway, here are my four favourites!
First on our list is Dictyocaulus viviparus, the bovine lungworm, which has a quite fantastic means of getting about. To set the scene, the momma worm is living in the cow’s lungs, lays some eggs, which the cow kindly coughs up, swallows, and the craps out. So the poor little parasite is now embedded in a big pile of cow turd on the ground, where it has the pleasure of hatching from its egg. Now this baby parasite would quite like to get to another cow, so it can have babies of its own, but what self-respecting cow is going to eat its own crap. Perhaps it would be best off getting off this steaming pile that it calls home, and finding some grass, but how? This is the fantastic part, as it turns out that a species of fungus (Pilobolus spp) grows on the cow dung, and when it’s ready to send out its spores, it does so in an explosive fashion. So our little baby worm climbs onto the fungus, waits until it sporulates, then rides the explosion out onto the grass! Truly fantastic I’m sure you’ll agree.

Our second fantastic parasite is called Onchocerca, and our more knowledgeable readers may question this designation, as it causes River Blindness in Africa, a far from fantastic disease. However, what is fantastic is how this worm avoids being killed by the immune system. To grasp the beauty of its evasiveness, we must first learn a small amount about how the human body kills invaders. Parasites such as Onchocerca are attacked using a type of cell known as an eosinophil, whereas bacteria are generally destroyed by another type, called neutrophils. These two types of cell are pretty specific in their killing, so neutrophils are useless at killing parasites. Now brace yourself for the fantasticness! Onchocerca worms allow bacteria to live beneath their cuticle (skin), so the body finds these bacteria, and despatches neutrophils to kill them. It also notices the worm, and sends out eosinophils to kill them. However, the response to the bacteria surrounds the worm with neutrophils, which block the eosinophils from reaching their target, protecting the worm from the immune attack. Further, the worm’s cuticle protects the bacteria from being killed, so the worm can sit happily in a protective cocoon of neutrophils, kindly provided by the human’s own immune system.

Next up we have the first of our mind-controlling parasites, Toxoplasma gondii, a protozoon parasite, that can cause disease in immuno-compromised humans, such as those with AIDS, but is in fact generally transmitted between cats and mice. Now for this parasite to complete its life cycle, it requires the infected mouse to be caught by a cat, which represents a small problem, as mice are usually repelled by the smell of cat urine, keeping them away from cat hunting grounds. This is but a small problem for Toxoplasma though, as it “simply“ alters the mouse’s behaviour, making it attracted to cat urine. Thus, mouse is more likely to be caught by a cat, completing the parasite’s life cycle.

Our second mind-controlling parasite is a liver fluke of cattle, which goes by the name of Dicrocoelium dendriticum. Its life cycle is complex, but involves first a snail (Galba truncatula), and then an ant (Formica spp.), with the ant being eaten by a cow to complete the cycle. Another small parasitic problem…ants tend to live either underground, or on the surface of the ground, but cows tend to eat tall grass. How then can we get the cow to eat the ant. Well we could do this by getting the ant to stop being repelled by light (negatively phototrophic), and instead be attracted to it. So the stage of the fluke found in the ant (the cercariae), send some emissaries to the ant brain, where they encyst to become metacercariae. This causes a lesion in the ant brain, changing its behaviour, so it’s attracted to light, and climbs tall grass blades to get as close to the sun as possible. A perfect target for a cow to eat.

Don’t emotions make wonderful post titles? Don’t answer that. Anyway, next week is one that can only be described as filling me with trepidation, for two reasons: 1) The dreaded exam results, 2) Placement at London’s equine hospital. I can’t even think which one scares me more, but I’ll stick with my usual motto of “cross that bridge when we get to it.” I’ll keep all none of you posted on how they both go anyway…

P.S. I promise this is the last post with an emo title, I’m really not that man!

One of the seven deadly sins if you believe in all that, and I came damn close to it today!  Not once, but twice!  EMS, or extra-mural studies is the work placement component of the vet course, and there are 26 weeks of it to do, all in “holiday time.”  Now to be fair, it’s generally good fun, and there’s a lot to be learnt, so I’ve no problem with actually doing it.  What I hate, however, is the organising part…and to be specific, organising the farm practice part.  As it turns out, there don’t appear to be many farm vets within an hour’s drive of either my rented house, or my parents house.  Those that there are, are already full of students far more organised than me!  Anyway, after getting through at least 10 practices that claimed to do farm work in the Yellow Pages, but had packed it in, or were full, my patience was wearing a little thin.  Visions of having all my placements organised for me flashed before my eyes - Lo! For I was a Bristol student!  Fortunately, it was but a fleeting vision, before I quickly realised I’d rather graduate with a degree that meant something… (for those of you who aren’t aware, Bristol were recently given 2 years to improve standards, or their right to produce veterinary graduates would be suspended!)

Fortunately, a few more phone calls did the trick, and the summer’s fun was sorted.  The next task for today was the dreaded dentist.  Fortunately, all was fine, and a quick 5 minutes of running a probe over my teeth seemed to quell the man’s desire to cause pain.  Unfortunately, the receptionist was not so easily pleased - for this 5 minute visit, the princely sum of £15.90 was demanded!  Forgive me if I’m being naive, but I thought this was an NHS dentist?  Anyway, that sin came back to me all to quickly when I realised this equated to an hourly rate of £190.80.  Compare this with a certain Australian equine clinician, with more letters after his name than I’ve had hot dinners (OK, I was a packed lunch kid, but it’s still a fair few) , who declares an hour of his time to be worth in the region of £100.  Was I really jealous of a mouth-obsessed torturer?  Well I came close, I’m man enough to admit that, but after experiencing the joys of drilling teeth in dead dog’s heads, there’s no way I could do that to a live human!  No, for that I’d need at least 200 quid an hour!

…and welcome to the Veterinary Parasite, named dually because of the author’s status as both a vet student, and a parasite!  Feeding off the tax-payer’s hard-earnt, while pissing it up the wall and doing no work.  Yeah right.  Anyway, if you decide to keep reading you can look forward to not only a chronicle of my experiences in the clinical stages of the course, but an added bonus - rants about any particular subject that gets my goat! Oh, did I not mention animal puns as well? No? Well, a veritable herd of animal puns will be coming your way.

So sit down, make yourself comfortable, and we shall begin.