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| Spirocerca lupi | |
|---|---|
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| Spirocerca lupi egg. | |
Scientific classification  | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Nematoda |
| Class: | Chromadorea |
| Order: | Rhabditida |
| Family: | Spirocercidae |
| Genus: | Spirocerca |
| Species: | S. lupi |
| Binomial name | |
| Spirocerca lupi (Rudolphi, 1809) | |
| Synonyms [1] | |
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Spirocerca lupi is a species of nematode. [2] In dogs, infestation can cause sarcoma of the esophagus. [3] Doramectin has been used against it. [4]
S. lupi is endemic (occurs naturally) from southern Africa all the way up to Israel, Turkey, Greece and India; faecal evidence also exists for it in the southern USA. Although early reports of the disease were American1-3, few reports emerge any longer from this country. This may be because a commonly-used insecticide wiped out a of the hosts, before being banned – so never reached Israel or SA (anecdotal). This parasite has a complex 110-day life cycle with both intermediate and paratenic (=transport) hosts. Coprophagous (“dung”) beetles are the intermediate hosts, ingesting the eggs which contain the L1 larvae. Within this host, the eggs encysts and develop into the infectious L3 larvae in 2 months. The infectious process can be direct (ingestion of an infected beetle) or indirect (ingestion by a paratenic host[1] such as wild birds and poultry, lizards and rodents, rabbits and even hedgehogs). Thus both lizards and bird offal may be important sources of infection, although there is no proof, as some maintain, that hadidah ibis faeces are infectious. The paratenic hosts are more probable sources of infection for domestic dogs.
There is no particular predilection by age or gender. In one study4, older, sterilised female dogs were overrepresented amongst patients with malignant transformation of oesophageal nodules to sarcomas. In another, Labradors and other large-breed dogs were overrepresented.5 Although due to the length of the lifecycle, infection is rare in patients under 6 months of age, puppies as young as two months of age may die due to massive migrations causing aortic aneurysms and/or pyothorax.6 Although cats are normally not thought to be susceptible, in fact vomiting has been reported as a consequence of S. Lupi infection in this species.7
Once ingested, the L3 excyst in the stomach acid of the dog within hours and break through to the serosal surface within a day or two. The L3 larvae take about a week to 10 days reach the thoracic aorta via the coeliac arteries. Once in the aorta, they reside here for up to 3 months, maturing to the L4 stage, before migrating over the next few months to the caudal thoracic aorta. They migrate in the wall of the aorta, causing it potentially serious scarring and damage. This migration can result in sudden and catastrophic aortic rupture / aneurysm (possibly with higher infective doses), or be asymptomatic. These pathognomonic features are the most consistent signs of spirocercosis.
(life cycle image)
Having undergone their final moult, once the L5 (adult) worms reach the oesophageal submucosa they mature, breed and the females lay microscopic eggs. Males and females are distinguishable by 2 months post infection, but the oesophageal nodules take 3 to 9 months to develop. The female creates an opening in the mucosa, but then moves back into the submucosa or muscularis to complete development. Up to 2,000 eggs/gram faeces/day are passed out into the interior of the oesophagus and into faeces via the small opening which looks like a reddened nipple on endoscopy. Generally, about 2000 eggs/gram of faeces are passed, with the peak egg-laying period being about 5 and 7 months post-infection. The adult worms can remain viable for up to 2 years in the nodule.
The presence of the worm causes severe irritation to the oesophagus and it responds by laying down fibrous scar tissue and inflammatory tissue – a type of “pre-fibroma”. Although not a tumour, a suppurative prefibroma, or multiple fibromata, can be quite bulky – even larger than a grapefruit in some patients – and cause many problems. Patients typically having 1 – 4 granulomata, each with 6 – 30 worms. Initially the nodule tissue is actually more akin to an abscess/fibroma tissue with fibrin, fluid, loose connective tissue and necrosis; as it transforms into a malignant nodule, giant cells increase and activation of inflammatory cells becomes more prominent.8
Spondylitis, a typical sign ascribed to spirocercosis, is thought to arise from aberrant migration of some of the larvae leaving the aorta. Spondylitis is highly specific for spirocercosis. It has even observed that the intraspinal migration of worms can cause a typical “acute intervertebral disc” syndrome.9-11 It has been described that some dogs develop salivary gland necrosis as a result of presumptive vagal afferent dysfunction12-14 (similar to the pathogenesis of hypertrophic osteopathy)4 , 5, 13 . They may also develop pyothorax, and S. lupi should be considered a potential cause for this syndrome.
Licensed treatments for Spirocercosis include:
Unlicensed treatments include the use of weekly doramectin or ivermectin injections.
Efficacy of treatment should be confirmed by radiography and/or follow-up endoscopy.
Sialoadenitis responds to treatment with phenobarbitone.
Patients with permanent megaoesophagus may required lifestyle alterations
Large nodules can be excised surgically although this is complex surgery requiring a specialist team.
Patients with neoplastic transformation of the tumours require chemotherapy; doxorubicin is thought to be the most effective drug for this, although no large trials exist to confirm this.
Patients with hypertrophic osteopathy (Marie's Disease) may respond to surgical removal of the chest mass or vagotomy.
Patients in endemic areas should also be tested for co-infection with Dirofilaria repens, as inadvertent treatment of this generally innocuous disease can cause dramatic and sometimes fatal consequences. Use of a macrocyclic lactone "net" strategy may reduce this risk.
In the earliest stages of infection, dogs may present with acute vomition, or have no symptoms whatsoever. Later on, with nodule formation, one obvious problem is in swallowing. Sometimes, dogs will vomit, retch or regurgitate. Other times, it may be more subtle. Dogs may just be inappetent; lick their lips; cry when swallowing; “cough” or “retch”; extend the neck; salivate; have diarrhoea; salivation; or submandibular lymphadenomegaly. Some dogs just lose weight but continue eating. Other patients may appear to present with polyarthritis (immune-mediated); vague, sometimes severe generalised or localised pain (even over the lumbar region).
Apart from the manifestations and consequences mentioned, the worm can also:
Firstly, the veterinarian must suspect Spirocercosis. Given its propensity for bizarre manifestations, this can sometimes be extremely challenging. Nonetheless, it can be diagnosed in most cases by a combination of careful questioning, thoracic radiographs, fibre-scope (endoscopic) evaluation of the oesophagus and stomach and special faecal flotation techniques (the standard technique is not usually adequate). In certain circumstances, CT scans of the chest; or exploratory surgery may be used for individual patients. Sometimes, the diagnosis is just a surprise. Standard faecal flotation techniques are inaccurate as egg laying is sporadic and affected by many factors, but modified sugar solution techniques and repeated floats (2 – 3 consecutive days) available from your veterinary laboratory can be 80% sensitive5. Eosinophilia is uncommon.
Faecal evaluation is readily available and in some hands, especially those using the sugar flotation technique of Markovics24, (as opposed to standard Zinc-Flotation techniques), diagnostic accuracy is very high (80% sensitivity). Most practices do not have this sugar solution or understand the technique and thus faecal flotation is not very sensitive. The Spirocerca eggs are light and small, and easily missed.
Radiography and CT (Computed tomography) are useful tools in the diagnosis of spirocercosis. Radiographically, the mass may be visualised in the caudal oesophagus; undulation of the aortic outline; thoracic vertebral spondylitis[1] in ¼ of patients (over mid-thoracic region); air-filled oesophagus; and other distant signs (such as aspiration bronchopneumonia, pulmonary metastases, mediastinitis, hypertrophic osteopathy). A pneumooesophagram or positive contrast oesophagram can be helpful in delineating the mass(es).17 An important factor is that the vet MUST take at least TWO orthogonal, thoracic views using a high kV (70 + 2 x cm thickness of chest) and low mAs (0.02) technique. Some authors have described the DV/VD evaluation of the aortic silhouette as the MOST accurate way of diagnosing spirocercosis on a radiograph, and spondylitis as an aid which increases sensitivity from 53% to 86%13. One third of patients have spondylitis. Do not confuse spondylitis with spondylosis. A right lateral radiograph is the preferred lateral view in South Africa, as the normal oesophagus cannot ordinarily be seen in this view.13 , 15
Endoscopy is close to 100% sensitive for the detection of this disease13, although again, some masses can be extra-oesophageal or, with inadequate insufflation of the oesophagus, completely undetectable. Patients undergoing anaesthesia for these procedures should not be premedicated with α2-agonists (medetomidine, xylazine) as this may raise aortic pressures and cause aneurismal rupture.18 It is important to us a methodical approach to gastro-oesophagoscopy; always start by advancing the scope to the stomach, retroflex the scope completely and check the inner cardiac sphincter for masses. Even a small 1 cm mass in this area can trigger profound vomition. Secondly, when doing oesophagoscopy, consider that you may not (a) have video-recording facilities and (b) you may need to rescope to assess response to treatment, particularly if this isn’t a good resolution of symptoms, and you may need to check for neoplastic transformation (evidence as ulceration and necrosis of the mass). In this instance, use a spirocerca mapping chart so that you can record “before” and “after” sizes, numbers, location and appearance of the mass. Write the distance to the lower oesophageal sphincter in the centre. T
If you are planning on performing surgery, or if there are questions about the aorta or neoplastic transformation, consider referring the patient to the university for a CT or CT angiogram. Knowing if the cardiac sphincter is involved is critical in making decisions about operability; and length of the involved oesophagus is also critical.
[1] Not spondylosis, which is a non-inflammatory, degenerative bridging osteogenic process between vertebrae; spondylitis occurs on the ventral body of the vertebra and is an inflammatory periostitis.
[1] A paratenic host carries the parasite mechanically but no biological change occurs during that carriage
Aortic dissection (AD) occurs when an injury to the innermost layer of the aorta allows blood to flow between the layers of the aortic wall, forcing the layers apart. In most cases, this is associated with a sudden onset of severe chest or back pain, often described as "tearing" in character. Vomiting, sweating, and lightheadedness may also occur. Damage to other organs may result from the decreased blood supply, such as stroke, lower extremity ischemia, or mesenteric ischemia. Aortic dissection can quickly lead to death from insufficient blood flow to the heart or complete rupture of the aorta.
An aortic aneurysm is an enlargement (dilatation) of the aorta to greater than 1.5 times normal size. They usually cause no symptoms except when ruptured. Occasionally, there may be abdominal, back, or leg pain. The prevalence of abdominal aortic aneurysm ("AAA") has been reported to range from 2 to 12% and is found in about 8% of men more than 65 years of age. The mortality rate attributable to AAA is about 15,000 per year in the United States and 6,000 to 8,000 per year in the United Kingdom and Ireland. Between 2001 and 2006, there were approximately 230,000 AAA surgical repairs performed on Medicare patients in the United States.
A thoracic aortic aneurysm is an aortic aneurysm that presents primarily in the thorax.
Gastrointestinal diseases refer to diseases involving the gastrointestinal tract, namely the esophagus, stomach, small intestine, large intestine and rectum, and the accessory organs of digestion, the liver, gallbladder, and pancreas.
A chest radiograph, called a chest X-ray (CXR), or chest film, is a projection radiograph of the chest used to diagnose conditions affecting the chest, its contents, and nearby structures. Chest radiographs are the most common film taken in medicine.
Spirometra is a genus of pseudophyllid cestodes that reproduce in canines and felines, but can also cause pathology in humans if infected. As an adult, this tapeworm lives in the small intestine of its definitive host and produces eggs that pass with the animal's feces. When the eggs reach water, the eggs hatch into coracidia which are eaten by copepods. The copepods are eaten by a second intermediate host to continue the life cycle. Humans can become infected if they accidentally eat frog legs or fish with the plerocercoid stage encysted in the muscle. In humans, an infection of Spirometra is termed sparganosis.
Eggs per gram (eggs/g) is a laboratory test that determines the number of eggs per gram of feces in patients suspected of having a parasitological infection, such as schistosomiasis.
Syphilitic aortitis is inflammation of the aorta associated with the tertiary stage of syphilis infection. SA begins as inflammation of the outermost layer of the blood vessel, including the blood vessels that supply the aorta itself with blood, the vasa vasorum. As SA worsens, the vasa vasorum undergo hyperplastic thickening of their walls thereby restricting blood flow and causing ischemia of the outer two-thirds of the aortic wall. Starved for oxygen and nutrients, elastic fibers become patchy and smooth muscle cells die. If the disease progresses, syphilitic aortitis leads to an aortic aneurysm. Overall, tertiary syphilis is a rare cause of aortic aneurysms. Syphilitic aortitis has become rare in the developed world with the advent of penicillin treatments after World War II.
Dioctophyme renale, commonly referred to as the giant kidney worm, is a parasitic nematode (roundworm) whose mature form is found in the kidneys of mammals. D. renale is distributed worldwide, but is less common in Africa and Oceania. It affects fish eating mammals, particularly mink and dogs. Human infestation is rare, but results in kidney destruction, usually of one kidney and hence not fatal. A 2019 review listed a total of 37 known human cases of dioctophymiasis in 10 countries with the highest number (22) in China. Upon diagnosis through tissue sampling, the only treatment is surgical excision.
Endovascular aneurysm repair (EVAR) is a type of minimally-invasive endovascular surgery used to treat pathology of the aorta, most commonly an abdominal aortic aneurysm (AAA). When used to treat thoracic aortic disease, the procedure is then specifically termed TEVAR for "thoracic endovascular aortic/aneurysm repair." EVAR involves the placement of an expandable stent graft within the aorta to treat aortic disease without operating directly on the aorta. In 2003, EVAR surpassed open aortic surgery as the most common technique for repair of AAA, and in 2010, EVAR accounted for 78% of all intact AAA repair in the United States.
Toxocara canis is a worldwide-distributed helminth parasite that primarily infects dogs and other canids, but can also infect other animals including humans. The name is derived from the Greek word "toxon," meaning bow or quiver, and the Latin word "caro," meaning flesh. T. canis live in the small intestine of the definitive host. This parasite is very common in puppies and somewhat less common in adult dogs. In adult dogs, infection is usually asymptomatic but may be characterized by diarrhea. By contrast, untreated infection with Toxocara canis can be fatal in puppies, causing diarrhea, vomiting, pneumonia, enlarged abdomen, flatulence, poor growth rate, and other complications.
Trichuris suis is a whipworm; the variations in thickness of the anterior and posterior segments give the parasite the characteristic "whip-like" appearance. Adult females measure 6 to 8 cm and adult males 3 to 4 cm. T. suis eggs are oval and yellow-brown with bipolar plugs. T. suis is also used in helminthic therapy studies.
Oesophagostomum is a genus of parasitic nematodes (roundworms) of the family Strongylidae. These worms occur in Africa, Brazil, China, Indonesia and the Philippines. The majority of human infection with Oesophagostomum is localized to northern Togo and Ghana. Because the eggs may be indistinguishable from those of the hookworms, the species causing human helminthomas are rarely identified with accuracy. Oesophagostomum, especially O. bifurcum, are common parasites of livestock and animals like goats, pigs and non-human primates, although it seems that humans are increasingly becoming favorable hosts as well. The disease they cause, oesophagostomiasis, is known for the nodule formation it causes in the intestines of its infected hosts, which can lead to more serious problems such as dysentery. Although the routes of human infection have yet to be elucidated sufficiently, it is believed that transmission occurs through oral-fecal means, with infected humans unknowingly ingesting soil containing the infectious filariform larvae.
Injury of the thoracic aorta refers to any injury which affects the portion of the aorta which lies within the chest cavity. Injuries of the thoracic aorta are usually the result of physical trauma; however, they can also be the result of a pathological process. The main causes of this injury are deceleration and crush injuries. There are different grades to injuries to the aorta depending on the extent of injury, and the treatment whether surgical or medical depends on that grade. It is difficult to determine if a patient has a thoracic injury just by their symptoms, but through imaging and a physical exam the extent of injury can be determined. All patients with a thoracic aortic injury need to be treated either surgically with endovascular repair or open surgical repair or with medicine to keep their blood pressure and heart rate in the appropriate range. However, most patients that have a thoracic aortic injury do not live for 24 hours.
Ground-glass opacity (GGO) is a finding seen on chest x-ray (radiograph) or computed tomography (CT) imaging of the lungs. It is typically defined as an area of hazy opacification (x-ray) or increased attenuation (CT) due to air displacement by fluid, airway collapse, fibrosis, or a neoplastic process. When a substance other than air fills an area of the lung it increases that area's density. On both x-ray and CT, this appears more grey or hazy as opposed to the normally dark-appearing lungs. Although it can sometimes be seen in normal lungs, common pathologic causes include infections, interstitial lung disease, and pulmonary edema.
Alaria is a genus of flatworms, or trematodes, in the family Diplostomidae.
Open aortic surgery (OAS), also known as open aortic repair (OAR), describes a technique whereby an abdominal, thoracic or retroperitoneal surgical incision is used to visualize and control the aorta for purposes of treatment, usually by the replacement of the affected segment with a prosthetic graft. OAS is used to treat aneurysms of the abdominal and thoracic aorta, aortic dissection, acute aortic syndrome, and aortic ruptures. Aortobifemoral bypass is also used to treat atherosclerotic disease of the abdominal aorta below the level of the renal arteries. In 2003, OAS was surpassed by endovascular aneurysm repair (EVAR) as the most common technique for repairing abdominal aortic aneurysms in the United States.
Anisakis simplex, known as the herring worm, is a species of nematode in the genus Anisakis. Like other nematodes, it infects and settles in the organs of marine animals, such as salmon, mackerels and squids. It is commonly found in cold marine waters, such as the Pacific Ocean and Atlantic Ocean.
Inflammatory aortic aneurysm (IAA), also known as Inflammatory abdominal aortic aneurysm (IAAA), is a type of abdominal aortic aneurysm (AAA) where the walls of the aneurysm become thick and inflamed. Similar to AAA, IAA occurs in the abdominal region. IAA is closely associated and believed to be a response to and extensive peri-aneurysmal fibrosis, which is the formation of excess fibrous connective tissue in an organ or tissue in a reparative or reactive process IAA accounts for 5-10% of aortic aneurysms. IAA occurs mainly in a population that is on average younger by 10 years than most AAA patients. Some common symptoms of IAA may include back pain, abdominal tenderness, fevers, weight loss or elevated Erythrocyte sedimentation rate (ESR) levels. Corticosteroids and other immunosuppressive drugs have been found to decrease symptoms and the degree of peri-aortic inflammation and fibrosis
Nematode infection in dogs - the infection of dogs with parasitic nemamotodes - are, along with tapeworm infections and infections with protozoa, frequent parasitoses in veterinary practice. Nematodes, as so-called endoparasites, colonize various internal organs - most of them the digestive tract - and the skin. To date, about 30 different species of nematode have been identified in domestic dogs; they are essentially also found in wild dog species. However, the majority of them often cause no or only minor symptoms of disease in adult animals. The infection therefore does not necessarily have to manifest itself in a worm disease (helminthosis). For most nematodes, an infection can be detected by examining the feces for eggs or larvae. Roundworm infection in dogs and the hookworm in dogs is of particular health significance in Central Europe, as they can also be transmitted to humans (zoonosis). Regular deworming can significantly reduce the frequency of infection and thus the risk of infection for humans and dogs.