Survey-based Study at Laboklin

The aim of the study was to identify the reasons for discontinuation of ASIT in horses during or after the induction phase (initial treatment, starter set).
The induction phase lasts approximately six months, which is considerably shorter than the recommended 12-month period for assessing the response to therapy.

Horses were selected from the ASIT treatment order lists of the Laboklin laboratory for the years 2021–2023, specifically those for whom no further ASIT treatments were ordered after the starter set. Of 4,271 initial treatments, 1,475 cases (34.5 %) did not receive any follow-up treatments.
To determine the reasons for discontinuation of ASIT, the treating veterinarians were contacted using written questionnaires. They could select one or more possible reasons. The collected data were analysed descriptively.

 

Reasons for ASIT Discontinuation

A total of 171 responses reporting 204 reasons for why no follow-up ASIT treatment was ordered after the initial treatment were analysed. Patients who did not receive further ASIT due to death (n = 15) were excluded from the analysis.
The horses included in the study exhibited the following symptoms: asthma (n = 68, 39.8 %), pruritus (n = 40, 23.4 %), urticaria (n = 3, 1.8 %), headshaking (n = 3, 1.8 %), or a combination of these symptoms (n = 31, 18.1 %). In 26 horses (15.2 %), the specific symptoms were not reported (Fig. 1).

The most common reasons for discontinuation of ASIT (Fig. 2) were loss of contact with the owner (n = 55, 27 %), lack of owner compliance (n = 40, 19.6 %), insufficient treatment response (n = 39, 19.1 %), or a good treatment response (n = 27, 13.2 %).

These four reasons accounted for over 80 % of treatment discontinuations. Other reasons included cost or sale of the horse (each n = 13, 6.4 %), adverse effects (n = 4, 2 %), and lack of knowledge regarding continuation of ASIT (n = 4, 0.5 %).

ASIT was also discontinued due to symptom improvement following a change of stable or optimisation of management (n = 7, 3.4 %) or a dietary change (n = 1, 0.5 %). In three horses (1.5 %), the induction phase had not yet been completed due to protocol adjustment, and in one horse (0.5 %), ASIT was continued but the ASIT manufacturer was changed.

In 116 questionnaires, it was reported that ASIT was administered according to the manufacturer’s protocol, while in four horses the protocol was individually adjusted. No additional symptomatic therapy was given in 93 horses; 11 horses received mucolytics alongside ASIT, 15 underwent inhalation therapy with glucocorticoids and bronchodilators, and six patients were treated with systemic glucocorticoids. In eight horses, it was reported that symptoms worsened again after ASIT was discontinued.

 

How Can ASIT Discontinuation Be Reduced and Treatment Success Optimised?

Induction treatments usually last for six months, which is considerably shorter than the recommended 12-month period for evaluating therapeutic success.

It can take up to a year for the full clinical benefit of ASIT to become apparent. In this Laboklin study, follow-up treatment was not ordered for over one third of initial treatments, resulting in premature discontinuation of ASIT after the induction phase.

 

Loss of Contact with Owners and Lack of Owner Compliance
The most common reasons for ASIT discontinuation were loss of contact between veterinarian and owner (27 %) and lack of owner compliance (19.6 %), together accounting for nearly 50 % of all discontinuations. In a Laboklin study on ASIT discontinuation in dogs, these were likewise the most frequently reported reasons. Owner compliance – the cooperation of the owner in implementing the recommended therapeutic measures – is a crucial factor for treatment success. Owners should be thoroughly informed about the treatment protocol, duration of therapy, the delayed onset of ASIT effects, and the expected costs, in order to align their expectations appropriately. Continuous communication is key to ensuring good owner compliance, particularly during the first year of therapy. Regular check-ups or telephone contact with owners not only maintain communication but also ensure continuous monitoring of the patient.

 

Treatment Success Lower than Expected
The third most common reason for ASIT discontinuation was insufficient therapeutic response (19.1 %). This was often reported in combination with poor owner compliance. Due to the delayed onset of ASIT effects, treatment success should be evaluated no earlier than one year after initiation.
Discontinuation of ASIT due to perceived lack of efficacy after the induction phase represents an issue of owner education, as these horses were prematurely classified as non-responders.
Veterinarians should clearly communicate the delayed onset of ASIT effects in order to manage owner expectations and prevent premature discontinuation during the first year of therapy.
In the current study, 93 horses reportedly did not receive any additional therapy, while only 15 horses were treated symptomatically during the induction phase of ASIT to alleviate allergic signs. Symptomatic treatments – such as glucocorticoids, antihistamines, bronchodilators, and mucolytics (in cases of equine asthma) – are often necessary during the first months of ASIT to rapidly reduce clinical symptoms until the effects of the immunotherapy take hold.
This approach is also an important factor in improving owner compliance. The duration and dosage of medications should be kept as low as possible. Symptoms should be reduced but not entirely suppressed, as complete suppression may obscure the need for protocol adjustment.
It is also important to correctly define treatment success. ASIT is considered successful if treated horses show an improvement of more than 50 % in clinical symptoms, or if the need for additional symptomatic medications can be reduced by more than 50 %. Before a horse is classified as a non-responder, it should be carefully evaluated whether there is truly no improvement. This requires precise documentation of the frequency of allergic episodes, as well as the duration and dosage of any additional symptomatic therapy. In this study, four respondents reported that ASIT was discontinued due to insufficient effect, but symptoms subsequently worsened after cessation. In these cases, it can be assumed that ASIT did provide clinical improvement that was not adequately documented, leading to the erroneous classification of these horses as non-responders.
The average success rate of ASIT in horses, according to a review by Herrmann et al. (2023), was 75 % for equine asthma, 88 % for urticaria, 59 % for pruritic dermatitis, and 36 % for sweet itch (ASIT using insect allergens only). Limited data are available regarding the efficacy of ASIT for allergy-in-duced headshaking; one study reported good to very good responses in five of the six horses included.
The reason why horses treated solely with insect allergens show lower success rates is not fully understood. One possible explanation is that, due to the simultaneous presence of different allergens, it is clinically difficult to distinguish between environmental pollen allergies and sweet itch (insect bite hypersensitivity). Many horses are polysensitised, and in these cases, additional allergens besides insects should be included in ASIT. Another theory is that insect allergens in ASIT may induce a weaker immune response compared with other allergens. This could be related to the fact that only whole-body extracts are currently available for ASIT, whereas treatments using pure insect salivary proteins might be more effective. This hypothesis is supported by studies using recombinant allergens in ASIT. A recent study by Graner et al. (2024) treated horses with ASIT consisting of recombinant Culicoides allergens. Clinical response was significantly higher than in the placebo control group, with almost 90 % of treated horses showing at least a 50 % improvement in symptoms in the second year of treatment.
The duration of the disease may also influence the success rate of ASIT. Hunsinger (2003) reported that horses treated with ASIT within two years of the onset of allergic symptoms responded significantly better to therapy. In horses with sweet itch, the success rate of ASIT was 75 % when treatment was initiated within the first two years after disease onset. This rate decreased considerably when the start of ASIT was delayed.
Another measure to optimise treatment success may be the individual adjustment of the protocol regarding injection volume and/or treatment intervals. In this study, protocol adjustment was reported in only four horses; all other patients were treated according to the manufacturer’s protocol.
Continuous patient monitoring is necessary to identify the need for protocol adjustment.

 

Discontinuation despite successful response
The fourth most common reason for stopping ASIT (13.2 %) was clinical improvement in the treated horses, leading to interruption of therapy. Most patients require long-term, often lifelong treatment to maintain control of allergic symptoms. Experience shows that symptoms typically recur after ASIT is discontinued. This was also observed in the present study in two patients whose ASIT was not continued due to marked improvement. Restarting ASIT can be demanding, often requiring repeated allergy testing, initiation of a new induction phase, and in some cases, a less favourable therapeutic response. Therefore, it is generally recommended not to interrupt ASIT in responders and to inform owners of the need for ongoing treatment. If clinical improvement is stable over several years during the maintenance phase, injection intervals may be gradually extended up to eight weeks.

 

Costs
In this study, costs were cited as the reason for ASIT discontinuation in 6.4 % of cases. For owners, the expenses associated with ASIT during the first year—including allergy testing and regular veterinary check-ups—may appear high.
However, in the long term, ASIT is considerably more cost-effective than purely symptomatic therapy, which can be very expensive in horses. Poorly controlled allergic horses often require more frequent veterinary visits, higher doses of symptomatic medications, and additional diagnostic or therapeutic interventions to manage potential side effects of these treatments. Providing this information can help motivate owners to continue ASIT throughout the first year of treatment and, during the maintenance phase, even in cases of moderate clinical response.

 

Side effects
In general, ASIT can be considered very safe in horses. In the present study, ASIT was discontinued due to adverse effects in four horses (2 %). In all cases, allergic symptoms worsened following the injections; additionally, one horse developed diarrhoea and another experienced circulatory problems. Worsening of allergic signs immediately after injections is one of the most common adverse effects, which was also observed in this study.
If this side effect occurs, the allergen extract dose should be reduced and the induction protocol individually adjusted. The importance of continuous communication between veterinarians and owners should be emphasised with regard to adverse effects. Owners should carefully observe their horses’ reactions to injections and immediately report any issues to the treating veterinarian to allow appropriate adjustments to the ASIT protocol.
The Laboklin team is available for consultation regarding protocol modifications.
Anaphylactic reactions (urticaria, angioedema, respiratory distress, circulatory collapse) are very rare. One horse in the current study experienced circulatory problems, leading to discontinuation of ASIT. The most common adverse effect during the induction phase is a self-limiting local reaction at the injection site; however, this was not cited as a reason for treatment discontinuation.

 

Conclusion

In summary, ASIT represents an important component of the multimodal management of allergic horses and is a lifelong therapy that requires close collaboration between owners and veterinarians. The first year of treatment necessitates intensive monitoring and constitutes the critical period for achieving therapeutic success. The most common reasons for discontinuation of ASIT are loss of contact with owners, poor owner compliance, and overly high expectations regarding rapid treatment effects. Improved education and communication, regular check-ups, and strict adherence to ASIT guidelines can increase the number of horses that respond successfully to ASIT and derive long-term benefit from the therapy.

 

Dr. Elisabeth Reinbacher

 

Our Services for Equine Allergies

• Screening tests
• Main tests for allergen differentiation (seasonal allergens, perennial allergens, insects, feathers/ hair/dander, feed)
• Screenings (allergy profiles – skin, allergy profile – respiratory)
• PAX complete (environmental allergens and/or food)
• Allergen-specific immunotherapy (ASIT)

Diagnosis
The diagnosis is based on clinical symptoms combined with histopathological examination.

Treatment
Due to the limited efficacy of immunomodulatory drugs, ECLE represents the most challenging form of cutaneous lupus erythematosus to treat. Cyclosporine, glucocorticoids, azathioprine, and leflunomide can be administered as monotherapy or in combination but are often ineffective. Consequently, more than half of the patients in previous studies were ultimately euthanized due to lack of therapeutic response.
There are some reports of successful use of alternative medications such as mycophenolate mofetil and high-dose oclacitinib in ECLE patients. Mycophenolate mofetil was successfully used in a German Shorthaired Pointer. High-dose oclacitinib (1.8 mg/kg/day) was described as an effective monotherapy in two reports involving a total of three patients. Notably, complete remission was achieved in a Magyar Vizsla treated with high-dose oclacitinib despite prior unsuccessful treatment with cyclosporine. Therefore, oclacitinib has been suggested as a possible standard monotherapy. However, another report documented the death of a female dog after four months of therapy with oclacitinib.

 

Mucocutaneous Lupus Erythematosus (MCLE)

Mucocutaneous lupus erythematosus (MCLE) has been described in German and Belgian Shepherd dogs of various ages. The primary differential diagnosis is mucocutaneous pyoderma.

Clinical symptoms
Ulcerative lesions commonly occur symmetrically in mucocutaneous areas. The perianal and perigenital regions are most frequently affected. Additionally, ulcers may appear on the lips or around the eyes (Fig. 3 and 4). Due to the ulcerative lesions in the perianal or perigenital region, these patients are often presented because of painful defecation or urination. Pruritus is generally absent or only mild in intensity.

Diagnosis
Since mucocutaneous pyoderma is the primary differential diagnosis, it should be excluded by cytological examination. Moreover, mucocutaneous pyoderma typically resolves with antibiotic therapy, which is not the case in MCLE patients. The
diagnosis should be confirmed by histopathological examination.

Treatment
The prognosis for MCLE is good, and treatment with prednisolone (2 mg/kg/day) can lead to rapid healing within one month. One report described successful use of oclacitinib in two MCLE patients.

 

Discoid Lupus Erythematosus (DLE)

Discoid lupus erythematosus (DLE) is the most common form of lupus in this category and is divided into two groups: facial or localized discoid lupus erythematosus (FDLE), in which skin lesions are confined to the head and neck, and generalized discoid lupus erythematosus (GDLE), where lesions also occur below the neck. The disease can occur at any age. Since most cases are worsened or possibly even triggered by UV light exposure, the condition was formerly referred to as nasal solar dermatitis or photosensitive nasal lupus.

Clinical Symptoms
The clinical signs of facial discoid lupus erythematosus (FDLE) typically begin with depigmentation, erythema, and scaling on the nose. These lesions can progress to erosions, ulcerations, crusts, and loss of the normal architecture of the planum nasale; the nasal bridge may also be affected (Fig. 5 and 6). Over time, these changes can spread to other sun-exposed areas such as the lips, pinnae, and periocular region.

Patients with generalized discoid lupus erythematosus (GDLE) may additionally show generalized or multifocal plaques and alopecia on the neck, back, and thorax. Both FDLE and GDLE can present with or without pruritus. Both forms of the disease are usually benign and do not exhibit systemic involvement.

Diagnosis
The diagnosis is based on the patient’s history, clinical signs, and histopathological examination.

Therapy
Patients ‒ like those with VCLE ‒ should be protected from sunlight, as UV exposure worsens symptoms. Topical tacrolimus ointment (0.1%) as monotherapy can be effective. If the response is insufficient, glucocorticoids combined with tacrolimus ointment may be administered. Cyclosporine is also an option. Successful treatment with oclacitinib has been reported in four dogs with FDLE.

 

Lupus-unspecific Dermatitis

Systemic lupus erythematosus (SLE) is a multisystem disease with diverse symptoms but lacks the histopathological features typical of cutaneous lupus erythematosus (CLE). Reported signs in SLE patients include joint disease,
haematologic abnormalities, glomerulonephritis, ulcerative stomatitis, and fever. Dermatologic manifestations such as scaling, mucocutaneous and oral ulcers, ulceration and/or hyperkeratosis of the paw pads, and alopecia may also occur. The prognosis is generally poor.

Dr. Amir Davoodi

Our services related to lupus diseases:

• Large screening + complete blood count
• Cytology
• Histopathology

Diagnosis of Diseases Causing Pruriceptive Pruritus

Pruriceptive pruritus is the most common mechanism of pruritus in dogs and cats.
Primary causes include ectoparasitic and allergic diseases. A third group consists of bacterial or Malassezia infections, which are often secondary to other skin conditions, complicating the diagnostic process. Additionally, any chronic skin disease presenting with lesions can also cause pruriceptive pruritus.

Sarcoptic Mange

• Sarcoptes Antibody Test (IgG): An ELISA test quantifies IgG antibodies in canine serum, with antibodies detectable approximately four weeks after infestation. Sensitivity is 85%, increasing to nearly 99% after four weeks of infestation, with a specificity of 90%.
• Sarcoptes PCR: Real-time PCR detects mites in extensive superficial skin scrapings from dogs, cats, ferrets, rabbits, guinea pigs, and other Canidae or Mustelidae species (reservoir: fox).

Feline demodicosis by Demodex (D.). gatoi

• PCR for D. gatoi: is postulated to be a highly effective test. As D. gatoi is not present in healthy cats, a positive result would be diagnostic. It is recommended that D. gatoi PCR be performed in all cats with pruritus before considering allergic disease.

Flea Allergic Dermatitis

• Flea Saliva Antibodies: A positive result indicates hypersensitivity to flea saliva. Compatible clinical signs alongside a positive test confirm the diagnosis. The test, offered as a single IgE test (Fcε receptor), as part of an allergy screening with mites, pollens, and fungi, or within comprehensive allergy profiles by Laboklin, uses native and recombinant flea saliva allergens for high sensitivity.

Food Allergy Diagnosis

• Food allergy diagnosis requires an elimination diet for two months to control clinical signs, followed by a challenge diet to confirm Serological food allergy testing measures allergen-specific IgE and IgG, with a negative predictive value of 81.1%.
  Foods without detected antibodies are suitable for elimination diets. Laboklin offers various food allergen panels, including the PAX Complete Food panel.

Atopic Dermatitis Diagnosis

• Atopic dermatitis is clinically diagnosed through detailed history and examination. Allergy tests identify causative allergens for avoidance or allergen-specific immunotherapy (ASIT) in cases of atopic dermatitis, insect hypersensitivity, or feline allergic asthma. Laboklin provides allergy panels, allergy profiles, the PAX complete environmental test, and allergen solutions for intradermal testing.

Pyoderma and Malassezia Dermatitis Diagnosis

• Cytology is the most relevant test for suspected pyoderma or Malassezia dermatitis, with Laboklin providing results within 24-48 hours of sample receipt.
• Bacterial cultures identify pathogens and guide antibiotic selection. Samples must be collected under sterile conditions to prevent contamination with normal flora. Bacterial and mycological swabs should be transported in suitable media. Bacteria are identified using MALDI-TOF mass spectrometry, and antibiograms determine antimicrobial sensitivity, including MRSP identification if necessary.

Epitheliotropic Lymphoma Diagnosis

• Epitheliotropic lymphoma can present with pruritus alongside exfoliation, ulceration, depigmentation, or nodules. Histopathological examination is essential for diagnosis.

 

Diagnosis of Diseases Causing Neuropathic Pruritus

Some neuropathic pruritus conditions are hereditary, such as Acral Mutilation Syndrome (AMS) observed in several breeds, and Sensory Neuropathy (SN) in Border Collies. In these cases, a genetic test (PCR) is essential for confirming the diagnosis.
Laboklin offers a comprehensive panel of genetic tests, including those for the aforementioned conditions.

 

Diagnosis of Psychogenic Pruritus

When psychogenic pruritus is suspected, it is crucial to first rule out any dermatological or internal diseases that could be causing the pruritus. Once these have been excluded, referral to a veterinary behaviour specialist (ethologist) is recommended for further assessment and management.

 

Treatment of Pruritus

The treatment of pruritus is essential from the very first moment, aiming to relieve clinical signs and improve the animal’s condition. In cases of severe pruritus, treatment should begin even while investigating the underlying cause.

Treatment approaches include both reactive and proactive strategies:

• Reactive Treatment: controls pruritus during acute phases of disease.
• Proactive Treatment: maintains control after resolving acute signs, preventing relapses in conditions like atopic dermatitis.

 

Systemic Treatment Options

• Glucocorticoids: These anti-inflammatory drugs are effective and fast-acting but should be used cautiously to avoid side effects. Commonly used are oral prednisolone or prednisone, with dosages tailored to individual needs.
• Oclacitinib (Apoquel®): A JAK-STAT inhibitor that targets IL-31, providing rapid relief for allergic pruritus. It is safer than glucocorticoids and particularly effective for atopic dermatitis in dogs.
• Lokivetmab: This monoclonal antibody neutralizes IL-31 and is administered subcutaneously every four weeks. It is a safe and effective option for proactive management of atopic dermatitis.
• Cyclosporin: An immunosuppressant that inhibits calcineurin, cyclosporine is ideal for long-term management of allergic conditions. It requires an initial loading dose followed by maintenance therapy and can be combined with other treatments during flare-ups.

Conclusion

Pruritus, whether acute or chronic, demands effective management to alleviate suffering and improve quality of life. Identifying and treating the disease is essential for long-term success.
Collaboration between general practitioners and specialists ensures optimal care, providing relief for affected animals and their owners alike.

 

Dr. Carmen Lorente, DVM, PhD, DipECVD
EBVS® European Specialist in Veterinary Dermatology 

 

Services on the topic

• Pruritus Profile small/medium/large
• Allergy pre-test and main tests
• PAX complete (environmental allergens, feed)
• Flea Saliva, Sarcoptes Ab, Malassezia Ab, Staphylococcus Ab
• Demodex-PCR, Sarcoptes-PCR