The Killer Worm!
Recently, one of our most handsome young customers, a 4 year old Lab, managed to contract this ugly and nasty little creature. In general, there are five main types of worms that can affect your fur kids;- roundworms, tapeworms, hookworms, whipworms and heartworms. The mother of roundworms is known as Spirocerca Lupi (see: S. lupi is endemic (occurs naturally) from southern Africa all the way up to Israel, Turkey, Greece and India (Wikipedia)), and is also one of the few worms that cannot be controlled using natural or herbal dewormers. It is, unfortunately, also one of the worms that can kill your fur kids.
This little-know parasite has gained great public audience in recent years, but is not a new parasite, according to Professor Joop Boomker, of the Department of Veterinary Tropical Diseases, University of Pretoria (see: DogWorld (Article)). Rosalind Stone (Hospital Manager and Veterinary Nurse), wrote that “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.” (see: Spirocerca lupi – The “worm in the throat” – Some Veterinary info (Article)).
Spirocerca Lupi is a worm that completes its life cycle in dogs and causes severe, potentially life-threatening diseases. Your fur kid can pick up this worm through intermediary hosts – from eating beetles or small animals such as mice, rats, lizards, wild birds and, most notably, the common Hadeda. 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.
It is a worm that for quite some time was assumed to be limited to rural areas, especially where there are cattle and sheep. But considering the increase in Hadeda populations in Gauteng, it could explain the prevalence of the condition in urban areas, where most dogs never leave their own gardens and are fed, by and large, under roof.
What does it do once inside the dog?
Rosalind wrote “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.”
She continues “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?
Rosalind points out “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.
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.”
How is it treated?
Unfortunately, in most of cases, current available treatment is usually not effective. This is because diagnosis is usually made only when clinical signs indicate the existence of a problem. By this time, the granuloma will be quite large and there is a high chance that it has already become cancerous.
There are remedies available, which are always administered and supervised by a veterinary surgeon. These are known as macrocyclic lactones; however, it must be emphasized that they should not be used on Collies or Collie crosses, which are highly intolerant of macrocyclic lactones.
It also seems that the only drug that truly work on this devil infestation is doramectin (Dectomax). More about research on Spirocerca lupi (roundworm) (see: Follow-up survey of the prevalence, diagnosis, clinical manifestations and treatment of Spirocerca lupi in South Africa (JSAVA)). There is some research available on milbemycin oxime as alternative drug treatment (see: Successful Resolution of Esophageal Granulomas in a Dog Infected with Spirocerca lupi (PubMed)).