Spirocerca lupi – The “worm in the throat” – Some Veterinary info

 

 

Compiled by: Dr Liesel van der Merwe, Valley Farm Animal Hospital, Pretoria.

 

Spirocerca lupi – The “worm in the throat”
A worm called Spirocerca lupi is becoming more common in South Africa’s summer rainfall
areas, leading to an almost endemic situation. This worm lives in the dog’s oesophagus where it
forms a nodule. Many worms can live inside a nodule and numerous nodules can form.
The female lays eggs and these are passed in the stool of the dog (host). These eggs have to
be eaten by a dung beetle (intermediate host) for the lifecycle to continue. The small dung
beetles (scarab beetles) living in the stool are part of the lifecycle, not the dung rollers we are
more familiar with. he beetle can be eaten by the dog or another small mammal. The egg
hatches and matures to a larval stage three in the beetle and stays in that phase even if eaten
by other small mammals, lizards or birds. Further maturation will only occur if the host (beetle or
transport host) is eaten by a dog.
The third stage larvae hatch and burrow into the stomach wall where they migrate along the
arteries back towards the chest portion of the aorta, the main blood vessel in the body. This
takes about two weeks. Once in the aortic wall, the worms mature and stay there for about three
month. Extensive damage is caused to the aorta during this period and aneurysms develop.
These may rupture and cause acute death. Once the worms are mature, they migrate directly
across the body tissues to the oesophagus which lies adjacent in the chest. At this stage these
worms are about 4-5 cm long and can cause considerable damage, resulting in rupture of large
blood vessels, inflammation of the lining structures of the lungs and infection. The worms then
establish themselves in the oesophagus where they live, mate and lay eggs.
Dogs react differently to these nodules: some dogs, especially fox terriers, show signs of sever
irritation with even small nodules (gagging, swallowing, retching) whereas other dogs may show
no symptoms until the nodules are large. Other symptoms associated with the migration can be
fevers, joint pain, coughing, and difficulty breathing. With time, and due to the chronic irritation
caused by the worm in the tissue, these nodules can become cancerous. This is a serious
condition which may or may not respond to surgery depending on the extent of the cancer.

 

Diagnosis is best made by doing an oesophageal endoscopy (putting a camera into the oesophagus) and observing for a nodule. Chest X-rays can also help, but may miss some
nodules. Not all nodules grow into the oesophagus and a CT scan might also be used to check
for these. The worm sometimes gets lost and can make nodules in just about any organ. This is
called aberrant migration. If one of your dogs is diagnosed with this worm it is advisable to have
all your other dogs checked.
Preventative therapy is not yet proven beyond a doubt but evidence shows that you will
decrease your chances of re-infection by 80% if you deworm your dogs monthly with a
dewormer containing milbemycin oxime (Milbemax®), or use a cattle dewormer doramectin.
These anti-parasiticide agents are the only proven drugs to cure and decrease the infection with
Spirocera lupi. Spot-on preparations containing these drugs do exist, but there is no evidence
that they are effective in treating spirocercosis. Worms that are exposed to these drugs also lay
fewer eggs, even before they die, thus decreasing environmental contamination.
Deworming your dog monthly is the preferred method of controlling all other worms (round and
tapeworm) as their lifecycles are about 21 days long and monthly deworming prevents them
from maturing and laying eggs, contaminating your environment. This disease has not been
documented to affect humans, and only rarely cats. So take the bull by the horns with this
devastating disease and get your dogs checked by your veterinarian and start a monthly
preventative program. My dogs are on it . .

 

 

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If you would like to read further, and view some images, please visit https://petpatch.net/spirocerca-lupi-infection-in-dogs

8 Responses to “ Spirocerca lupi – The “worm in the throat” – Some Veterinary info ”

  1. Carmen Tietjens says:

    Just read the article about the worms. I know the signs and symptoms may not always be obvious…(also think part of the article was left out…from “oesophagus)”
    Would I be looking for obvious nodules…..or could these worms present themselves in the dogs stool??

  2. Carolyn says:

    HI Carmen

    with this condition you won’t see anything from the outside which is the scary thing. Once the nodules have formed you can then pick it up when they regurgitate food, cough, etc. You won’t see worms in the stool but if a vet did a wet prep of the stool they may see eggs under the microscope.

    I am not sure how the article appeared for you but from what I can see the full article is there?

  3. Tanya says:

    There was half a sentence missing on :
    Diagnosis is best made by doing an oesophageal endoscopy (putting a camera into the oesophagus)and observing for a nodule. …
    but i’ve fixed it :)

  4. Spirocerca lupi in Dogs

    By Rosalind Stone

    When I was a student studying veterinary nursing at Onderstepoort all those years ago our professor of entomology said that although we should take note, it was unlikely that we would ever actually see a case. Over the intervening decades, however, the incidence of Spirocerca lupi in dogs has risen sharply, most notably during the past few years, and especially in KZN and Gauteng, although it is suspected that fewer cases are being reported in the other provinces simply because it is not being correctly diagnosed.

    Recent events have caused me to do some in depth research and I am fairly convinced that it is widespread and far more common than originally suspected.

    What is it and how is it spread?

    It is a worm which is spread by various species of dung beetles, and for quite some time it was assumed to be limited to rural areas, especially where there are cattle and sheep. However more recent research indicates that this is not necessarily the case and an increasing number of urban dogs are presenting with the condition. One theory is that declining standards in our abattoirs is allowing infected animals to pass through the system, effectively ending up on your plate and in your dogs bowl! NEVER feed your dogs’ raw meat of any description! (and consider adopting a vegan diet yourself – sorry, just indulging in a passion of mine!)

    Further research by the clever doctors at Onderstepoort now reveals that certain animals may be acting as intermediary hosts – these include lizards, mice, wild birds and, most notably, the common Hadeda, which would explain the prevalence of the condition in urban Johannesburg, where most dogs never leave their own gardens and are fed, by and large, on commercial dry dog food.
    Dogs become infected through eating the intermediary host, or its faeces, or through picking up the worm eggs which remain on the lawn and in pastures.

    What does it do once inside the dog?

    These are clever little blighters who like to travel, beginning their journey in your dogs’ stomach, they then migrate into the aorta (the biggest blood vessel in the body) where they hang around for several weeks, maturing. While many dogs show no symptoms during this phase, the thinning of the aortic wall can cause an aneurism or rupture, in which case a perfectly healthy dog will die, typically within a matter of minutes! Unless a complete autopsy is performed, including extensive examination of the chest cavity, the cause of sudden death will remain a mystery.

    When the worms have matured to the next stage they embark on another journey, most typically into the oesophagus (the pipe connecting the mouth to the stomach) During this migratory phase dogs may have an unexplained fever as the body fights off infection around the minute holes which have been bored through the oesophageal wall. A blood smear will reveal increased White Blood Cells indicating that the body is waging war! There may be no other symptoms at this stage although most dogs will go off their food as a result of the fever and generally feeling unwell.

    Once in the oesophagus the worms burrow into the wall and continue to grow, forming nodules within the tube, most frequently above and behind the heart. Obviously these nodules cause pain and irritation, and eventually begin to block the passage of food into the stomach. At this point the dog may begin to vomit, or regurgitate after eating, or simply show a preference for soft foods. They might also turn away from their bowl before they have finished eating as the sensation of food in the oesophagus becomes uncomfortable. However this often only manifests once the nodules have reached a substantial size: one positively diagnosed dog in Cape Town showed no loss of appetite or vomiting, but was presented to the vet because he brought up a small amount of bile during the night, almost every night, and the owners got tired of mopping it up every morning! He clearly just had severe “heartburn” as a result of the lesions, which was causing him to cough up the bile, and the intensive tests revealed Spirocerca lupi.

    Once the mass in the oesophagus reaches a certain size it will be impossible for the dog to swallow, and he will loose weight and become listless. In a number of cases these nodules become cancerous and then there is little that can be done to save the dog.

    In retrospect I suspect that several dogs in Nuwerus may have been suffering from Spirocerca lupi: clinically the dogs were emaciated, ate only small amounts of food, but had no fever or biliary. On examination there was also no obvious pain in the mouth or abdominal pain and/or blockage. In at least three cases I was unable to hear heart sounds and the dogs were showing difficulty in breathing. When the number of worms breaking through into the oesophagus increases there is a higher risk of infection leaking into the chest cavity and causing a pyothorax! Unfortunately when they were taken to the vet by AACL volunteers, all were euthanased without a proper diagnosis being made (Please note: this is not a criticism as the decision not to undergo expensive tests was well justified, coupled with the fact that information supplied by the owners is often unreliable. I mention it purely because it supports the theory that cases are simply not being diagnosed, as opposed to the myth that the condition does not exist!)

    Sometimes, however, the journey does not go according to the text books, and worms end up in other parts of the body. Very occasionally they might settle in other blood vessels and cause problems there, but they also sometimes migrate into the vertebral column (spine, back bone) where they may present as prolapsed discs or an intervertebral abscess: the dog will obviously show pain, especially when jumping in and out of the car, or onto furniture, or if pressure is put on that particular area. For some reason this seems to be more common in German Shepherd Dogs, who have a propensity for prolapsed discs and spondilitis anyway, which might again cause the presence of Spirocerca lupi to be overlooked.

    Another symptom in advanced cases is thickening/swelling of the legs – this is called Marie’s Syndrome and occurs as a result of pressure on the nerves as they pass through the chest cavity. In this case the pressure will be as a result of large nodules, which can reach the size of a grapefruit!

    How is Spirocerca lupi accurately diagnosed?

    Although it is a worm the normal diagnostic method of faecal flotation is unreliable for two reasons: firstly the eggs tend to be heavy and drop, and secondly because relatively few eggs are discharged, meaning that the test may have to be repeated at daily intervals for a week or even more.

    Barium X-rays will sometimes show the lesions and nodules in the oesophagus, usually in the space between the heart and the stomach, especially if the condition is advanced and the nodules are quite large. In areas where the vets are seeing several cases this is often used as diagnostic proof and the treatment is started. Sometimes the vet will send the dog to a specialist physician for an endoscope and biopsies, but this can be hugely expensive and beyond the budget of many dog owners.

    Sadly a great number of cases are only diagnosed on autopsy but since many owners elect to get on with their grieving without ever knowing the cause of disease or death, autopsies are not routinely performed.

    What can you, as owner, look out for?

    • Any reluctance to eat, or preference for soft foods, or wanting to eat but turning away after only a small amount
    • Pausing or hesitating before drinking water
    • Licking the lips and swallowing repeatedly in the absence of food (as if something is stuck in the oesophagus)
    • Excessive licking of the paws – this is due to a tingling sensation associated with Marie’s Syndrome mentioned above, but before the swelling becomes apparent.
    • Swollen salivary glands or excessive salivation (drooling from the mouth, over and above the normal drool appropriate for the breed!)
    • Unexplained, intermittent high temperature
    • Pain in the spine or lameness
    • Vomiting and regurgitation
    • Dyspnoea or difficulty in breathing, may be due to displacement of the trachea or an infection within the thoracic cavity.

    What is the treatment?

    If you notice any of the above symptoms take your dog to the vet and mention that you are concerned about exposure to Spirocerca lupi. I will stick my neck out here and suggest that if your vet laughs at you, either urge him/her to look at the latest findings from Onderstepoort or go to another vet! (please don’t tell your vet I said so)

    Although the mortality rate is high this is largely due to the condition not being timely diagnosed. The most effective treatment is through the administration of a drug called doramectin which must be injected by your vet (the recommended dose is available from OP) over a period of several weeks. However this drug is not registered for use in dogs and there is a very small risk involved (Onderstepoort is aware of very few adverse reactions and several vets are using it routinely without any problems)
    PLEASE NOTE: UNDER NO CIRCUMSTANCES MUST THIS DRUG BE GIVEN TO COLLIES, BORDER COLLIES, AUSTRALIAN CATTLE DOGS OR ANY OF THE HERDING BREEDS – THEY HAVE A SPECIFIC GENE AND ARE UNABLE TO TOLERATE IT! This may or may not include German Shepherd Dogs – there is a test for the gene marker but it may be safer to go with the slightly less effective alternative.

    If properly treated the dogs regain full health, and the nodules themselves reduce in size over a period of time. In resistant cases it may be necessary to repeat the course of treatment.

    What can you do to prevent it?

    • Never feed raw meat of any description
    • Be aware of exposure – if your dogs walk where there have been livestock, look out for the symptoms mentioned above. Also if you have Hadedas visiting your garden. In KZN the beaches are suspected of being a source of infection too, and there is no reason why this shouldn’t be the case in the Cape too.
    • In areas when a great number of cases are being seen, vets are recommending a prophylactic course of treatment every 6 months
    • Although this is a nematode (worm) ordinary de-worming tablets will not kill Spirocerca lupi, with the exception of Milbemax (milbemycin) which is available only from your vet. Unfortunately it will not kill the adult worms, and is only effective during the development stages. For this reason it should be given every three months as a preventative measure.

    Please feel free to pass this on to all your dog-loving friends, wherever they may be in the country. Should you have any queries you are welcome to email me at rosalinds@telkomsa.net.

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  7. Adri Minnaar says:

    My spaniel was diagnosed based on xrays showing the nodules in his oesophagus and stomach, luckily only there. He only eats rice and chicken at this stage. Since he started with treatment on Wednesday (the weekly injection, prednisone, lethyl and his antibiotics) he is looking quite better although the lethyl gives him a droopy, sleepy look. But whereas his faeces was runny up until Wednesday it’s almost as if he is blocked or constipated now, his stomach is swollen and he is uncomfortable because of the fact that his stomach didn’t empty itself since Wednesday. Is this normal, should I be concerned or should I just relax as an overprotective parent and wait for the meds to do its job??

    The vet told me that the prognosis is really good I have nothing to worry about as we caught it early enough.

  8. Mike says:

    My Hungarian Vizsla has not been right for 5 days now. He has pain in his neck and is holding himself very strangely at times. X-rays show nothing in abdomen, neck, or spinal issues. Bloods are normal too. Ultrasound came back normal as well. At the vets daily, we’re based in Cape Town. Would be keen to know anyone with any similar experiences. Thanks.

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