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Lauren Hughes, DVM
Anaplasmosis is an infectious disease affecting horses most commonly during tick season. A majority of cases are reported in California but it has also been identified all over the United States and worldwide including right here in New England. Knowledge of this disease and early recognition can greatly improve the prognosis for your horse.
This disease can affect horses of all ages and the clinical presentation can vary greatly depending on the duration of illness. Horses with Anaplasmosis can display a large variety of clinical signs ranging from a high fever (103-105 F), depression, decreased appetite, mild limb swelling, reluctance to move, icterus, and in rare cases incoordination/ataxia. The fevers are normally highest in the first few days of infection but can persist up to 12 days. Icterus, a build up of bilirubin, leads to a yellowing most commonly appreciated on the sclera of the eyes and oral mucous membranes. It is important that your veterinarian perform bloodwork while working up a horse with icterus as any disease process affecting the liver can also lead to icterus and should be ruled out in a case of Anaplasmosis.
Anaplasmosis is a tick borne disease caused by the bacterium Anaplasma phagocytophilum. This bacteria is carried by the deer tick, the same tick that carries and spreads Lyme disease. A horse becomes infected with the bacteria through the bite of a tick and it enters the blood stream where it lives within white blood cells. The organism acts to cause destruction of red blood cells, white blood cells and platelets and low levels of these cells are often seen on bloodwork when working up a horse with Anaplasmosis.
There are multiple ways to diagnose this disease with the most definitive being identification of the organism within the white blood cells on a blood smear. Even in cases of active infection, the bacteria may only infect a small number of cells so it is not always visualized. Titers can also be performed to assess immune response and confirm exposure to the bacteria. Lastly polymerase chain reaction (PCR) tests can be performed to recognize the DNA of the bacterium. Routine blood work may also be consistent with the disease process and show decreased red blood cell, white blood cell and platelet levels. In many cases it is difficult to obtain an immediate diagnosis so treatment if often initiated prior to confirming infection.
Early recognition of the disease and treatment with appropriate antibiotics often leads to a good prognosis and full recovery. Administration of a tetracycline antibiotic can be done intravenously or orally and can include oxytetracycline, doxycycline or minocycline depending on the individual case. In most cases fever and other clinical signs will dramatically improve within 48 hours of initiating antibiotics. Some horses with a mild form of the disease may recover without treatment but can also relapse within a few weeks so treatment is highly recommended. Banamine or other anti-pyretics are often used to help control the fever.
More severe cases with neurologic signs often require supportive care and may benefit from corticosteroid treatment.
Prognosis is excellent if the disease is recognized early and treatment is initiated. In more severe cases where neurologic signs develop additional treatment may be needed and permanent injury may occur due to incoordination/ataxia. Fatality is rarely reported due to this disease unless secondary complications occur.
There is currently no vaccine for this disease. Immunity is acquired after infection and normally lasts around two years following an active infection. The most important aspect of disease prevention is tick control by routinely checking your horses for ticks and removing them. Topical products are also available that can help against ticks.
If you have any questions or concerns regarding Equine Anaplamosis do not hesitate to contact the doctors of New England Equine Medical & Surgical Center.
Fig 1. Icteric Sclera: https://s-media-cache-ak0.pinimg.com/originals/3b/f8/bf/3bf8bfdcfba519c86e25c93dba303247.jpg
Fig 1. Icteric MM: https://www.vetstream.com/images-equis/thumbs/21_165672-thumb.jpg
Fig 2. Bloodsmear: https://anokaequineblog.files.wordpress.com/2014/03/morula.jpg
Merck Vet Manual. Webpage. <http://www.merckvetmanual.com/mvm/generalized_conditions/ equine_granulocytic_ehrlichiosis/overview_of_equine_granulocytic_ehrlichiosis.html>.
Reed, Bayly and Sellon. Equine Internal Medicine- 3rd Edition. St Louis: Elsevier, 2010. Print
Basics of Lameness
The 411 on the Basic Lameness Exams - Written by Dr. Laura Wodzinski
Equine lameness is an important and prevalent area of equine medicine. Whether solving a hoof abscess or diagnosing a meniscal tear in a stifle, the basic fundamental principles of a lameness work up apply. This article will cover the basic first steps of a lameness evaluation in addition to a few of the most common nerve blocks your veterinarian may perform.
When assessing a horse with a lameness, it is important to proceed with an approach that is methodical as well as cost effect. For this reason, many veterinarians begin with basic palpation and baseline lameness examination. On palpation, your veterinarian is looking for areas of heat, swelling, joint or tendon sheath effusion, increased digital pulses, or any areas that are sensitive or reactive to palpation. Depending on the degree of lameness, horses are trotted in straight lines and circles on hard ground and soft footing for the baseline lameness assessment. The variation in lameness depending on the surface can help determine soft tissue origin or bone, as soft tissue pathologies are often accentuated in the soft footing. The degree of lameness is evaluated on a scale set by the American Association of Equine Practioners (AAEP). This is a scale of 0-5 with 5 being the most severe lameness.
After achieving this baseline lameness, flexion tests can be performed based on the baseline lameness findings. A flexion test is when specific joints or regions of a limb (lower versus upper) are flexed for several seconds and then the horse is trotted off immediately. An increase in lameness after flexion helps to narrow down the region of interest to be the source of the pain. Additionally, hoof testers may be used to check for sensitivity in the foot. By squeezing the hoof capsule in several areas and evaluating the horses’ response perform this test, the areas of sensitivity can be determined if the horse tugs his leg away from the stimulus. Depending on the location of sensitivity, further diagnostics can be used to focus on these areas.
After identifying the affected limb(s) with a lameness evaluation, your veterinarian may decide to proceed with regional nerve blocks. These blocks are typically performed starting distally, or lowest on the limb, and working up the limb as the blocks desensitized everything below where the needle is inserted. There are various local anesthetic drugs that can be used for nerve blocks, however the most popular is Carbocaine (mepivacaine). This medication takes approximately 10-15 minutes to begin working and has a duration of action of approximately 2 hours. After allowing the block to begin taking effect, the horse is trotted again to evaluate the effect of the nerve block. An improvement in the lameness indicates the block desensitized the source of pain. Below is a list of common nerve blocks starting from the block lowest on the limb.
Palmar Digital Nerve block (PDN): This block is performed just above the heel bulbs on the inside and outside palmar/plantar digital nerves. The following structures are desensitized:
· >Caudal third to two-thirds of the sole, including the heel bulbs>
· >Navicular bone and bursa>
· >Palmar coffin and pastern joints>
· >Distal sesamoidean ligaments, deep digital flexor tendon and sheath>
· >Frog corium and digital cushion>
· >Wings of the coffin bone>
Abaxial Nerve block: Performed just below the fetlock joint on the inside and outside of the limb, this nerve blocks desensitizes the dorsal and palmar branches of the palmar nerve. In addition all of the areas affected by the PDN block, the abaxial block desensitizes the following major locations:
· >The long pastern, short pastern, and coffin bones>
· >Entire corium and sole>
· >Dorsal branches of the suspensory ligament>
· >Digital extensor ligament>
· >Possible diffusion into the fetlock joints and proximal sesamoid bones>
Low 4 Point: This block requires instillation of block in four different locations above the fetlock joint. The palmar and palmar-metacarpal nerves are blocked by inserting needles between the deep digital flexor tendon (DDFT) and suspensory ligament (SL) and just below the button of the splint on the inside and outside of the limb. In addition to all of the structures previously mentioned in the PDN and abaxial blocks, the Low 4 point block desensitizes the following structures:
· >Coffin, pastern, and fetlock joints>
· >Deep digital flexor sheath>
· >Soft tissue structures of the pastern and foot>
Joint Blocks: Certain joints may be blocked in order to get a very specific block when the area of pathology is suspected to be articular. Joint blocks require aseptic preparation as the needle and Carbocaine will be injected directly into the joint.
The information that can be obtained from a basic lameness examination, flexions, and nerve blocks can give the information needed to decide on further diagnostics. Radiographs and ultrasound are the most common diagnostic modalities used in equine lameness, however advanced imaging such as magnetic resonance imaging (MRI), computerized tomography (CT), and nuclear scintigraphy (Bone scan) are also very informative. MRI and CT will need to be performed under general anesthesia due to the necessity of the horse being absolutely still.
Lameness work-ups are an essential part of the equine health care. This common systematic approach can help localized the affected area to focus diagnostic efforts and make the correct diagnosis and treatment plan.
1. "LAMENESS EXAMS: Evaluating the Lame Horse." American Association of Equine Practitioners. N.p., n.d. Web. 09 Nov. 2016.
2. Service, Field. "Diagnostic Anesthesia." Diagnostic Anesthesia. N.p., n.d. Web. 09 Nov. 2016.
3. Vandenberghe, Aurelie. "Tenogenically Induced Allogeneic Mesenchymal Stem Cells for the Treatment of Proximal Suspensory Ligament Desmitis in a Horse." Frontiers. Front. Vet. Sci., 22 Oct. 2015. Web. 09 Nov. 2016.
Equine Gastric Ulcer Syndrome
Dr. Kathy Samley
>>>>>Equine gastric ulcer syndrome is a common condition in horses and foals. While any horse can develop gastric ulcers, they tend to be more common in horses in high levels of work. Studies have shown that the prevalence of gastric ulcers can be as high as 60-90% in show horses and thoroughbred racehorses. The equine stomach consists of two sections, the squamous (non-glandular) portion and the glandular portion. The two sections are separated by a line called the margo plicatus. Ulcers in the squamous portion of the stomach develop from the excess production of gastric acid, which damages the squamous mucosa leading to the development of an ulcer. The glandular portion of the stomach has a protective coating that contains bicarbonate and other substances to buffer the gastric acid, making it less prone to ulceration than the squamous portion. Ulcers in the glandular part of the stomach are less well defined and research is still being done to investigate their causes and pathophysiology. Risk factors for development of gastric ulcers include feeding a high starch diet, feeding a large amount of grain at a time, strenuous exercise, and stressful events such as traveling or illness. Gastric ulcers can present with a wide variety of different signs depending on the horse. Common signs include changes in behavior, decreased performance or reluctance under saddle, poor appetite, mild weight loss, and mild episodes of colic.>
How are gastric ulcers diagnosed?
The only way to definitively diagnose gastric ulcers is with a gastroscopy procedure. This procedure can be done either on the farm or in the hospital. The horse must be fasted overnight so that their stomach is empty for the procedure. For the exam, the horse is sedated and a small camera is passed up the horse’s nose, down the esophagus, and into the stomach. The stomach is then inflated with air so that the entire stomach can be visualized. The parts of the stomach that are examined include the cardia (entrance to the stomach), the greater and lesser curvature, and the pylorus (where the stomach exits into the small intestine). Before the gastroscope is removed, the extra air is removed from the stomach to prevent colic due to gastric distension.
Gastric ulcers are graded on a scale of 1-4 based on their severity. Grade 1 ulcers are the most mild and consist of areas of reddening or hyperkeratosis of the mucosa. Grade 4 ulcers are the most severe and consist of extensive or actively bleeding ulcers.
How are gastric ulcers treated?
The main treatment for gastric ulcers is omeprazole, commonly known as Gastrogard or Ulcergard. Omeprazole is a proton pump inhibitor which blocks the enzyme that releases gastric acid into the stomach and therefore helps to decrease the acidic environment of the stomach. For most ulcer types, typical treatment includes administering a full tube of omeprazole once a day for 28 days. Before the end of the omeprazole treatment, a recheck gastroscopy is recommended to ensure complete healing of the ulcers. For severe ulcers, sucralfate may be used as part of the treatment regimen. Sucralfate binds to the ulcer and forms a protective barrier from the acidic stomach environment.
How can I help prevent my horse from developing gastric ulcers?
If your horse is prone to gastric ulcers, there are several steps that can be taken to help prevent recurrence of ulcers in the future. A preventative dose of omeprazole (250 lb dose or ¼ tube for a 1000 lb horse) can be given before stressful events such as traveling, competitions, or switching barns. Since omeprazole takes three days to reach its full effect, this should be started at least three days prior to the event and continued for the duration of the event. Feeding a higher fiber, low starch diet will lower the gastric pH, and help to prevent ulcers. Hay or pasture should be made available as frequently as possible. Feeding hay in a nibble net is a good way to provide continual access to small amounts of hay throughout the day. If possible, hay should be fed before grain meals to provide a buffering effect. Additionally, there are many supplements available that contain antacids. These supplements can be fed with every grain meal to help buffer the acidic environment of the stomach.
Esophageal Obstruction in the Horse
Written by Intern Dr Laura Wodzinski
Imagine you just finished feeding your horses and are heading out of the barn when you hear coughing. You go to investigate further and find that in addition to the retching, Mr. Ed has feed material coming out of his nostrils and is salivating excessively. What should you do next?
Call a veterinarian!
Mr. Ed is most likely experiencing an esophageal obstruction, or choke. Choke severity can be very variable depending on the what the horse is choking on and the reason for the choke. When you first recognize a choke has happened remove all feed, hay, and water. Further attempts by the horse to drink or eat could increase their risk of aspirating foreign material into their lungs and subsequently developing a pneumonia.
Why do horses choke?
There are several factors that can predispose a horse to choking. Geriatric horses are commonly associated with choke since they often have poor dentition and decreased saliva production. Horses that bolt their food can be at greater risk of choke, especially when fed a pelleted grain that expands in the lumen of the esophagus when it comes in contact with the saliva. For these horses, placing large rocks in their feed bin can force them to eat around the rocks and slow down their intake. Other factors that can play a role in choking is feeding a sedated horse. Horses can choke on any feed material including beet pulp, hay, pelleted feed, or bedding. The two most common regions of the esophagus where feed material gets obstructed is the proximal esophagus, or the part closest to the head, and the segment just cranial to the thoracic inlet, or the region just before the esophagus enters the rib cage.
Do we need to do the Heimlich maneuver?
Luckily, to relieve choke we do not need to perform the Heimlich maneuver. Initially, your veterinarian will sedate the horse to lower their head, reduce anxiety, and relax the esophageal muscles. A long nasogastric tube is passed into their esophagus until resistance is felt, presumably the area of obstruction, and water can be used to lavage the obstruction while gently pushing it towards the stomach. It will be important to keep their head down as much as possible while relieving the choke to decrease the risk of the horse aspirating any liquid. Additional medications, such as Buscopan, can be used to relax the esophagus to aid in the movement of the food bolus. Another theory, is giving a drug to decrease smooth muscle tone such, as oxytocin. This drug can be associated with transient abdominal discomfort and sweating and is not safe to use in pregnant mares.
If these initial steps do not resolve the choke, the veterinarian may need to provide intravenous fluids to maintain adequate hydration since you horse will be unable to drink water while choked. Additionally, if the choke cannot be relieved with sedation, general anesthesia may be needed to get more relaxation and a more aggressive lavage. If all attempts to dislodge the choke are unsuccessful, surgical management can be pursued as an emergency procedure.
What are the complications that can be associated with a choke?
A common complication of choking is aspiration pneumonia, or an infection in the lung caused by inhaling food particles and material. Prophylactic antibiotic administration, either with oral tablets or injectable formulations, are typically prescribed following a choking incident to prevent this possible serious complication. It is important to monitor your horse for coughing, increased respiratory rate, appetite, lethargy, and fever for 5-7 days following a choking incident so you catch the early signs of pneumonia. If there is great concern for aspiration, a thoracic ultrasound can be performed to look at the lining of the lungs. Additionally your veterinarian will want to listen to the horse's lung sounds to see if there are any crackles or wheezes which are an indication of pathology in the. Factors that increase the risk of aspiration pneumonia include the duration of the choke, more attempts to drink while choked, and the horse having their head elevated while choking..
With a more difficult choke, an endoscopic examination, or passing a camera through the horses nose and into their esophagus, may be warranted. By visualizing the esophagus on the camera, the integrity of the esophageal tissue can be assessed for irritation or damage that can be associated with choking. When there is damage to the esophageal tissue, the area will heal by laying down scar tissue. This scar tissue is less elastic than the healthy esophageal tissue and can form a stricture, or narrowing of the esophagus. If a stricture forms then food passage down the esophagus will continue to be an issue and a feeding program will need to be adjusted accordingly.
Days Following the Resolution of Choke
After a horse has choked it will be important to introduce food very gradually and as a soupy gruel. The esophagus will need to have time to heal therefore making the food into a slurry will make passage through the esophagus easier. Prophylactic antibiotics as well as an anti-inflammatory drug, such as banamine, will typically be prescribed following the incident. Additionally, rectal temperature monitoring and close monitoring for signs of pneumonia will be crucial in recognizing any post-choking complications. A first time choke incident with no complications has an excellent prognosis. With complications of stricture or aspiration pneumonia, the prognosis decreases.
Understanding Equine Cellulitis
By Lauren Hughes, DVM
Cellulitis can be a relatively common and frustrating condition affecting the limbs of horses. The condition results from inflammation and infection of the subcutaneous tissues that lie beneath the skin. It commonly affects only one limb at a time and is most likely in the hind end.
The typical presentation of cellulitis is very prominent swelling of a limb that is often associated with lameness. The lameness is normally quite severe, with some horses even refusing to bear weight on the limb, and owners notice that it develops quite rapidly. Either areas of the limb or the entire limb will swell up and can reach 2-3x the normal size. The affected limb often becomes very warm and painful to the touch, and pitting edema may be present. A fever may be present and the horse may exhibit other signs of not feeling well including being lethargic and off feed.
Cellulitis cases can have no known trigger or may follow an insult including surgery, joint injections, wounds or trauma. The most common bacteria to be isolated from these cases are Staphylococcus spp. which normally inhabit the skin. These bacteria then can enter the deeper tissues and lead to infection through some break in the skin barrier. Edema in these tissues then forms when the bacteria and the toxins they release create an inflammatory response. This leads to blood vessels and lymph vessels becoming leaky and tissue building up in the subcutaneous tissue.
It is very important to get your veterinarian involved when a case of cellulitis is suspected as prompt diagnosis and treatment are crucial to successful recovery. Your veterinarian may suspect cellulitis on physical examination when a horse has a swollen, warm, painful limb and is exhibiting prominent lameness. It is important to rule out other causes of severe lameness and limb swelling including joint infections and fractures as well. Supporting diagnostics are then used to confirm and assess the extent of the condition. Ultrasound can be very useful in looking at the subcutaneous tissues and highlighting the presence of edema, seen as fluid accumulation within the tissue layers. Bloodwork will often show an elevation in the fibrinogen level, a marker used to assess inflammation, and/or changes to white blood cell counts.
The main stays of cellulitis treatment focus on eliminating the infection from affected tissues and supportive care to decrease the limb swelling. Broad spectrum antibiotics are commonly used to help clear the infection. NSAIDs can also be used to help control any pain and inflammation. Hydrotherapy with cold hosing, bandaging, sweat wraps and hand-walking or lunging are often crucial components of treatment and are used in combination to help reduce the swelling of the limb. Treatment can often be quite frustrating as many of these cases can take a while to resolve and full resolution is not always achieved.
Prompt and thorough treatment is very important in these cases as devastating and life threatening complications can follow a case of cellulitis. Some horses undergo very severe and deep infections that cannot be corrected with medical management alone and surgical debridement or drainage is necessary. In other cases, thrombosis of vessels can occur which leads to necrosis of tissue and skin sloughing wounds. These wounds can involve important underlying structures and may require a long and expensive period of intensive wound care and bandaging to resolve. Lastly, laminitis can occur in the affected limb due to damage to the coronary band or can develop in the contralateral limb due to the extra stress placed upon that limb.
Although survival rates are quite high and treatment is often successful, prognosis for a full recovery is not guaranteed. Some horses may have recurrence of the infection or suffer from lameness when returning to normal work loads after the initial episode. Chronic cases will often lead to a permanently thicker leg due to the presence of scar tissue. This can permanently affect the horses’ ability to normally drain the lymphatic system. Client compliance and early detection are crucial in recognizing chronic recurring cases and prompt treatment will help prevent episodes from progressing. Horses that are prone to recurring episodes are often maintained on strict exercise programs and extra care is taken to ensure proper hygiene and prevent exposure to infections.
If you have any other questions regarding cellulitis, please feel free to contact New England Equine Medical & Surgical Center.
Barr, Bonnie. Cellulitis. Rood & Riddle. 2011.Webpage.
Fig 1: Cellulitis. Anoka Equine Veterinary Services. 4 August 2014. Webpage.
Getman, Liberty M. Alternative Therapies for Cellulitis. ACVS Proceedings. 2011. Print.
Holmes, Peter. Lymphangitis in Horses. Merck Veterinary Manual. 2011. Webpage.
Reed, Bayly and Sellon. Equine Internal Medicine- 3rd Edition. St. Louis: Elsevier, 2010. Print.
Habronemiasis: A Sore Summer Topic
Habronemiasis goes by many names such as summer sores, jack sores, swamp cancer or bursatee. Habronemiasis is very common in horses in the South Eastern U.S., but can be seen in other areas of the country. Larvae of the stomach worm Habronemaspp. cause this skin disease. The adult nematodes cause parasitic infestation in the stomach of the horse, which is part of the nematode’s lifecycle. Infestation of the adult stomach worms is called gastric habronemosis, and it rarely causes clinical signs aside from a mild gastritis (stomach inflammation). The cutaneous form of the disease is caused by larvae of the stomach worm that get deposited into a wound or moist areas of the body by the fly (the intermediate host), and cause significant skin reactions. The larvae emerge from flies that feed on wounds or secretions from around the eyes or genital region. The most commonly affected areas are the corner of the eye (where tearing occurs), the sheath and urethral process of the male horse, and occasionally the lower extremities. These are also the areas where horses cannot ward off these vector flies by the swishing of their tail. The migration of the larvae in the tissue causes a hypersensitivity reaction as the larvae start to die. This reaction is granulomatous in nature. Horses are very good at developing what is colloquially known as ‘proud flesh’, which is an excessive development of a type of very vascular tissue called granulation tissue. It is part of the horse’s immune defense but often causes delayed wound healing due to the exuberant, extensive nature and overgrowth of the tissue. Thus, these sores take on the characteristic of ulcerative, nodular and tumorous masses (See Figure 1).
Figure 1: Cutaneous habronemiasis at common locations in the horse. From left to right ocular habronemiasis at the medial canthus of the eye, genitalia habronemiasis on the urethral process and sheath of a male horse. Photos courtesy of Atlanta Equine Clinic.
Diagnosis is based on clinical signs of non-healing ulcerative granulomas, which occur normally in the aforementioned locations. They often appear greasy, and reddish-brown in color. Occasionally you can see small (rice-sized) yellow calcifications, which are the dead larvae residing in the lesion. The only way to truly confirm habronemiasis is to take a biopsy of the affected tissue. Other skin lesions that can have a similar clinical appearance include squamous cell carcinoma, equine sarcoids, overgrowth of granulation tissue (proud flesh) following a wound, rain scald or ringworm. Thus, definitive diagnosis obtained by a skin biopsy is ideal in guiding treatment and future prevention. Skin scrapings and cytology rarely show larvae, and confirm a diagnosis. Biopsies, however, often show the larvae as well as an eosinophilic infiltrate, which is a type of local white blood cell reaction that occurs with parasite infection.
Treatment by prevention is ideal as these skin lesions can be very difficult to eliminate. Prevention predominantly involves fly control. By decreasing the horse’s exposure to flies this disrupts the Habronema lifecycle. These prevention measures include the frequent use of fly repellents, and adequate and careful disposal of horse manure. The eggs reside in the manure, and therefore, removal of manure will decrease the incidence of flies ingesting the egg, and then incubating the larvae until infection in the horse occurs. Regular anthelmintic (de-worming) treatment is another method to prevent the lifecycle from perpetuating. There are some topical treatments that have varied effects. Organophosphates have been applied topically in attempt to kill the larvae. Topical corticosteroids and anti-inflammatories are often not curative, but may control inflammation in the area. At times surgical removal or cauterization of the exuberant granulation tissue is necessary. The treatment of choice is Ivermectin, which is an anthelmintic. After one dose any infection of the species in the stomach will be resolved, and subsequent doses will help to promote healing in the cutaneous tissue. Rarely, if the migrating larvae are not already dead at time of treatment, and Ivermectin is administered then there may be temporary exacerbation of the lesions as the larvae presumably die. Spontaneous healing can be expected at times after such administration.
Cutaneous habronemiasis that affects the genital area such as the prepuce (sheath) or the urethral process, and glans penis can be particularly difficult to treat. They appear as thick or firm and irregularly shaped masses, and are often referred to as ‘Kunkurs’. Clinical signs in this area can include bleeding readily on manipulation due to the vascular nature of the infected tissue, itchiness, and spraying or frequent and difficult urination. Spraying is especially common if the urethra is affected. It is common in colder regions for the lesions to disappear in the winter and recur or increase in size in the warmer summer months. Despite the similar pathogenesis, these lesions are difficult to treat and often require surgical removal or amputation. Again, Ivermectin treatment can prove beneficial in these cases.
Lastly, in ocular habronemiasis the lesions can progress to the conjunctiva of the medial canthus, the third eyelid, and the eyelid proper. Clinical signs in this manifestation include blepharospasm (excessive squinting), and severe epiphora (excessive tearing). Horses tend to rub these areas, and this causes more tissue damage, which in turn, creates more sites for potential larvae deposits. Again, corticosteroids may provide temporary relief, but the best method is prevention. A fly mask or roll on fly repellents for around the eye are an ideal way to prevent further spread, and infestation. Chronic sores may require surgical intervention.
Overall, it is important to closely inspect your horse in the summer months for any new wounds and skin abrasions. Quick and effective cleaning and topical treatment of these wounds can prevent Habronema larvae from seeding, and causing a much greater problem. In addition, fly control and regular anthelmintic therapies are key to preventing this difficult and debilitating skin condition.
Radostitis, Otto. Verterinary Medicine: A Textbook of the Disease of Cattle, Horses, Sheep, Pigs and Goats, 10th ed. Philadelphia, Saunders, 2007. PDF.
Knottenbelt, DC. Diseases and Disorders of the Horse, Saunders, 2003.
Kahn, C. The Merck Veterinary Manual, 10th ed. Kenilworth, Merck sharp and Dohme Corp, 2015.