Podcast
Questions and Answers
A horse presents with patchy haircoat, pruritus, and alopecia, and is diagnosed with lice. Why are other horses on the same property also observed for lice, even if they appear asymptomatic?
A horse presents with patchy haircoat, pruritus, and alopecia, and is diagnosed with lice. Why are other horses on the same property also observed for lice, even if they appear asymptomatic?
- Adult lice may act as asymptomatic reservoirs, potentially leading to further spread. (correct)
- Lice transmission requires direct contact, thus close proximity necessitates monitoring.
- Lice rapidly develop resistance to common treatments.
- Lice can only be accurately diagnosed via microscopic examination.
What diagnostic finding would be most indicative of Onchocerca hypersensitivity as the cause of a horse's pruritic dermatitis?
What diagnostic finding would be most indicative of Onchocerca hypersensitivity as the cause of a horse's pruritic dermatitis?
- Visualization of mites crawling on the skin
- A large number of eosinophils on a skin scrape
- Bacterial growth on a culture of a skin lesion.
- Negative skin scrapings with eosinophilic perivascular cuffing on histopathology (correct)
In a horse diagnosed with dermatophytosis, what makes systemic antifungal treatment unnecessary in most cases?
In a horse diagnosed with dermatophytosis, what makes systemic antifungal treatment unnecessary in most cases?
- Dermatophytosis is typically self-limiting, resolving within 1-6 months without medication. (correct)
- The side effects of systemic antifungals often outweigh the benefits for a superficial fungal infection.
- The zoonotic potential of dermatophytosis makes topical treatment the only safe option.
- Systemic antifungals have a narrow spectrum of activity and are often ineffective against equine dermatophytes.
An 18-year-old Quarter Horse gelding presents with crusting, occasional pustules, and ventral edema. The condition initially responded to dexamethasone, but has since become refractory. What is the most likely diagnosis?
An 18-year-old Quarter Horse gelding presents with crusting, occasional pustules, and ventral edema. The condition initially responded to dexamethasone, but has since become refractory. What is the most likely diagnosis?
A horse presents with scaling, crusting, alopecia, and subcorneal pustules that began on its head and have spread across its body. Which aspect of its history would most strongly support a diagnosis of pemphigus foliaceus?
A horse presents with scaling, crusting, alopecia, and subcorneal pustules that began on its head and have spread across its body. Which aspect of its history would most strongly support a diagnosis of pemphigus foliaceus?
What diagnostic approach would be lease useful in confirming a diagnosis of reticulated leukotrichia in a Quarter Horse?
What diagnostic approach would be lease useful in confirming a diagnosis of reticulated leukotrichia in a Quarter Horse?
Why should client education regarding the potential consequences of continued use of alcohol for tail rubbing on show horses be emphasized?
Why should client education regarding the potential consequences of continued use of alcohol for tail rubbing on show horses be emphasized?
After diagnosing a horse with chorioptic mange, which long-term management strategy is most important to emphasize to the owner to minimize recurrence, especially in draft breeds?
After diagnosing a horse with chorioptic mange, which long-term management strategy is most important to emphasize to the owner to minimize recurrence, especially in draft breeds?
During a herd outbreak of lice, why is it important to treat all horses despite some not showing clinical signs of infection?
During a herd outbreak of lice, why is it important to treat all horses despite some not showing clinical signs of infection?
A horse presents with a chronic, non-healing wound on its lower limb. The wound is ulcerated, granulomatous, and intensely pruritic, with multiple yellow gritty masses. Which of the following diagnostics would be most appropriate?
A horse presents with a chronic, non-healing wound on its lower limb. The wound is ulcerated, granulomatous, and intensely pruritic, with multiple yellow gritty masses. Which of the following diagnostics would be most appropriate?
What statement best captures the combined understanding of the epidermal and dermal involvement of equine sarcoids?
What statement best captures the combined understanding of the epidermal and dermal involvement of equine sarcoids?
Which of the following factors is most important when deciding whether to treat a confirmed sarcoid?
Which of the following factors is most important when deciding whether to treat a confirmed sarcoid?
How does the pathogenesis of sarcoids relate to Bovine Papilloma Virus (BPV)?
How does the pathogenesis of sarcoids relate to Bovine Papilloma Virus (BPV)?
What is the best approach for a horse diagnosed with photosensitization related to liver damage?
What is the best approach for a horse diagnosed with photosensitization related to liver damage?
When evaluating a horse for a skin condition, what historical detail would MOST strongly suggest a parasitic etiology?
When evaluating a horse for a skin condition, what historical detail would MOST strongly suggest a parasitic etiology?
Which diagnostic test would be the gold standard for diagnosing bacterial rain scald?
Which diagnostic test would be the gold standard for diagnosing bacterial rain scald?
Which of the following best describes the zoonotic potential of lice?
Which of the following best describes the zoonotic potential of lice?
Which of the following is the most appropriate approach for a horse with severe Culicoides hypersensitivity ('sweet itch')?
Which of the following is the most appropriate approach for a horse with severe Culicoides hypersensitivity ('sweet itch')?
Why is it necessary to use a topical treatment repeatedly when trying to treat lice?
Why is it necessary to use a topical treatment repeatedly when trying to treat lice?
Which of the following is an appropriate treatment for sucking lice?
Which of the following is an appropriate treatment for sucking lice?
A horse owner reports that their horse, normally kept in a pasture, has developed hives. What's the most important next step?
A horse owner reports that their horse, normally kept in a pasture, has developed hives. What's the most important next step?
Why is a skin scrape often not helpful in diagnosing insect hypersensitivity?
Why is a skin scrape often not helpful in diagnosing insect hypersensitivity?
What is the lifecycle of lice? How are the lice transmitted?
What is the lifecycle of lice? How are the lice transmitted?
Why is it important to know whether a skin issue is unique to only one animal?
Why is it important to know whether a skin issue is unique to only one animal?
Which of the following diagnostic tests is the most useful in diagnosing nodular necrobiosis?
Which of the following diagnostic tests is the most useful in diagnosing nodular necrobiosis?
What is an important anatomical location on the body that will help support a diagnosis of ulcerative lymphangitis?
What is an important anatomical location on the body that will help support a diagnosis of ulcerative lymphangitis?
What is the goal of treatment for a horse with chronic progressive lymphedema (CPL)?
What is the goal of treatment for a horse with chronic progressive lymphedema (CPL)?
When diagnosing Onchocerca, name a location on the animal where a lesion could be?
When diagnosing Onchocerca, name a location on the animal where a lesion could be?
With a new horse addition to the farm, name appropriate steps in regards to biosecurity?
With a new horse addition to the farm, name appropriate steps in regards to biosecurity?
A horse with papules along its limbs is diagnosed with Sporothrix schenckii. Why is this a zoonotic concern?
A horse with papules along its limbs is diagnosed with Sporothrix schenckii. Why is this a zoonotic concern?
Select the group at high risk for melanoma?
Select the group at high risk for melanoma?
Why are summer sores only seen during the summer months and not other times of the year?
Why are summer sores only seen during the summer months and not other times of the year?
What is the cause of sarcoids?
What is the cause of sarcoids?
With a horse with confirmed squamous cell carcinoma (SCC), when should you consider euthanasia?
With a horse with confirmed squamous cell carcinoma (SCC), when should you consider euthanasia?
A horse has nonpruritic raised areas on the external genitalia. What differentials should be considered?
A horse has nonpruritic raised areas on the external genitalia. What differentials should be considered?
If an animal has a growth on the dorsal midline that's a non-painful and non-pruritic hard mass, what diagnostic steps should be taken?
If an animal has a growth on the dorsal midline that's a non-painful and non-pruritic hard mass, what diagnostic steps should be taken?
Why would a client use dexamethasone or flunixin meglumine to treat hives?
Why would a client use dexamethasone or flunixin meglumine to treat hives?
What is the etiology of Hereditary Equine Regional Dermal Asthenia (HERDA)
What is the etiology of Hereditary Equine Regional Dermal Asthenia (HERDA)
Which factor most influences the initial approach to diagnosing equine dermatological issues?
Which factor most influences the initial approach to diagnosing equine dermatological issues?
Why is understanding the duration and progression of a dermatological condition crucial in equine diagnosis?
Why is understanding the duration and progression of a dermatological condition crucial in equine diagnosis?
How might a seasonal component to a horse's skin condition alter your diagnostic priorities?
How might a seasonal component to a horse's skin condition alter your diagnostic priorities?
What is the significance of determining whether a skin condition affects a single horse or multiple horses in a herd?
What is the significance of determining whether a skin condition affects a single horse or multiple horses in a herd?
How does a horse owner's report of 'obscure' prior treatments impact your diagnostic strategy?
How does a horse owner's report of 'obscure' prior treatments impact your diagnostic strategy?
Why is understanding the specific configuration of skin lesions important during a physical exam?
Why is understanding the specific configuration of skin lesions important during a physical exam?
How does the distribution of lesions (dorsal, ventral, limb) aid in diagnosing skin conditions?
How does the distribution of lesions (dorsal, ventral, limb) aid in diagnosing skin conditions?
What does the presence of skin lesions often indicate about general health?
What does the presence of skin lesions often indicate about general health?
Why is mineral oil used in skin scrapings for dermatological diagnosis?
Why is mineral oil used in skin scrapings for dermatological diagnosis?
What is a crucial consideration when preparing a skin biopsy sample for dermatological diagnosis?
What is a crucial consideration when preparing a skin biopsy sample for dermatological diagnosis?
What is the key principle behind using a 'minced preparation' in equine dermatological diagnostics?
What is the key principle behind using a 'minced preparation' in equine dermatological diagnostics?
Why is it important to consider a zoonotic origin in equine dermatological cases?
Why is it important to consider a zoonotic origin in equine dermatological cases?
What is the primary significance of identifying lice as host-specific parasites in horses?
What is the primary significance of identifying lice as host-specific parasites in horses?
A draft horse is diagnosed with Chorioptic mange. What aspect of its signalment MOST strongly relates to this diagnosis?
A draft horse is diagnosed with Chorioptic mange. What aspect of its signalment MOST strongly relates to this diagnosis?
Why is decontaminating premises and equipment advised in mange treatment?
Why is decontaminating premises and equipment advised in mange treatment?
What is the primary significance of identifying Culicoides as the vector in Onchocerca transmission?
What is the primary significance of identifying Culicoides as the vector in Onchocerca transmission?
What is the underlying immunological mechanism in Culicoides hypersensitivity (sweet itch) that drives the horse's reaction?
What is the underlying immunological mechanism in Culicoides hypersensitivity (sweet itch) that drives the horse's reaction?
What is the most critical aspect of managing insect hypersensitivity in horses, beyond immediate relief of clinical signs?
What is the most critical aspect of managing insect hypersensitivity in horses, beyond immediate relief of clinical signs?
Why might skin testing and blood tests be implemented in a case of suspected insect hypersensitivity?
Why might skin testing and blood tests be implemented in a case of suspected insect hypersensitivity?
In cases of equine pruritus, what is meant by 'secondary bacterial infections,' and why are they significant?
In cases of equine pruritus, what is meant by 'secondary bacterial infections,' and why are they significant?
What key historical detail differentiates tail rubbing due to pinworms from iatrogenic tail rubbing in show horses?
What key historical detail differentiates tail rubbing due to pinworms from iatrogenic tail rubbing in show horses?
What is the primary etiological agent responsible for Dermatophilosis (rain scald) in horses?
What is the primary etiological agent responsible for Dermatophilosis (rain scald) in horses?
Why is winter/spring a period of high occurrence for Dermatophilosis (Dermatophilus congolensis)?
Why is winter/spring a period of high occurrence for Dermatophilosis (Dermatophilus congolensis)?
What microscopic findings should be expected from an impression smear for suspected rain scald?
What microscopic findings should be expected from an impression smear for suspected rain scald?
What is a significant consideration when implementing systemic antibiotic treatment for rain scald?
What is a significant consideration when implementing systemic antibiotic treatment for rain scald?
A horse shows clinical signs of dermatophytosis. What would be most important to consider in developing an appropriate treatment and management plan?
A horse shows clinical signs of dermatophytosis. What would be most important to consider in developing an appropriate treatment and management plan?
What histopathologic finding is the most significant when diagnosing pemphigus foliaceus?
What histopathologic finding is the most significant when diagnosing pemphigus foliaceus?
What is a main goal in managing chronic progressive lymphedema (CPL) in draft horses?
What is a main goal in managing chronic progressive lymphedema (CPL) in draft horses?
Why is photosensitization commonly observed on white or lightly pigmented areas of a horse?
Why is photosensitization commonly observed on white or lightly pigmented areas of a horse?
What is the significance of identifying an 'anechoic center' upon ultrasound evaluation of a nodular skin lesion?
What is the significance of identifying an 'anechoic center' upon ultrasound evaluation of a nodular skin lesion?
In cases of ulcerative lymphangitis, what is the primary significance of Corynebacterium pseudotuberculosis?
In cases of ulcerative lymphangitis, what is the primary significance of Corynebacterium pseudotuberculosis?
When presented with a possible ulcerative lymphangitis case, what are the most important steps?
When presented with a possible ulcerative lymphangitis case, what are the most important steps?
What are kunkers?
What are kunkers?
What are the main components of treating a horse with pythiosis?
What are the main components of treating a horse with pythiosis?
What is the underlying cause of sarcoids?
What is the underlying cause of sarcoids?
What is the most important factor that determines the approach to treating a horse with a sarcoid?
What is the most important factor that determines the approach to treating a horse with a sarcoid?
What is the significance of surgical removal in treating sarcoids, and when is it most appropriate?
What is the significance of surgical removal in treating sarcoids, and when is it most appropriate?
What is the difference between leukoderma and vitiligo?
What is the difference between leukoderma and vitiligo?
How do treatment strategies differ for melanomas versus sarcoids in horses?
How do treatment strategies differ for melanomas versus sarcoids in horses?
Why is it essential to differentiate between Vitiligo and Leukoderma in equine dermatology?
Why is it essential to differentiate between Vitiligo and Leukoderma in equine dermatology?
During a routine exam, you discover a solitary, firm, non-painful nodule, approximately 8mm in diameter, on the withers of a horse. What is the MOST appropriate next step?
During a routine exam, you discover a solitary, firm, non-painful nodule, approximately 8mm in diameter, on the withers of a horse. What is the MOST appropriate next step?
A horse presents with crusting lesions and matted hair in a 'paintbrush' pattern during the winter months. Which of the following management changes would be LEAST beneficial?
A horse presents with crusting lesions and matted hair in a 'paintbrush' pattern during the winter months. Which of the following management changes would be LEAST beneficial?
What is the underlying mechanism by which Culicoides hypersensitivity is considered heritable in horses?
What is the underlying mechanism by which Culicoides hypersensitivity is considered heritable in horses?
A horse owner is considering using XXterra for their horse's sarcoid. What is the MOST important consideration when counseling them about this treatment?
A horse owner is considering using XXterra for their horse's sarcoid. What is the MOST important consideration when counseling them about this treatment?
What is the primary reason systemic antifungal medications are often deemed unnecessary in treating equine dermatophytosis?
What is the primary reason systemic antifungal medications are often deemed unnecessary in treating equine dermatophytosis?
A horse presents with a history of a chronic, non-healing wound with yellow masses. To achieve a definitive diagnosis, what diagnostics should be performed?
A horse presents with a history of a chronic, non-healing wound with yellow masses. To achieve a definitive diagnosis, what diagnostics should be performed?
A horse displays signs of photosensitization, but liver function tests are normal. What diagnostic tests should be performed FIRST?
A horse displays signs of photosensitization, but liver function tests are normal. What diagnostic tests should be performed FIRST?
A horse with multiple skin nodules along its limbs is diagnosed with Sporotrichosis. Why is it important to inform the owner of its zoonotic potential?
A horse with multiple skin nodules along its limbs is diagnosed with Sporotrichosis. Why is it important to inform the owner of its zoonotic potential?
What is the MOST critical factor in determining the treatment approach for a horse diagnosed with an equine sarcoid?
What is the MOST critical factor in determining the treatment approach for a horse diagnosed with an equine sarcoid?
While evaluating a horse's dermatological condition, you note tail rubbing. What historical detail differentiates pinworm-induced pruritus from iatrogenic pruritus common in show horses?
While evaluating a horse's dermatological condition, you note tail rubbing. What historical detail differentiates pinworm-induced pruritus from iatrogenic pruritus common in show horses?
Why is it diagnostically useful to know if a horse's skin issue is unique to only one animal on the property versus multiple?
Why is it diagnostically useful to know if a horse's skin issue is unique to only one animal on the property versus multiple?
Which of the following statements correctly relates the role of Bovine Papilloma Virus (BPV) to equine sarcoid development?
Which of the following statements correctly relates the role of Bovine Papilloma Virus (BPV) to equine sarcoid development?
While examining a horse with suspected Onchocerca, skin scrapings are negative. Which alternate diagnostic technique offers the BEST chance of confirming the presence of microfilariae?
While examining a horse with suspected Onchocerca, skin scrapings are negative. Which alternate diagnostic technique offers the BEST chance of confirming the presence of microfilariae?
Following confirmation of squamous cell carcinoma (SCC) on a horse's genitalia, what clinical scenario warrants strong consideration of euthanasia?
Following confirmation of squamous cell carcinoma (SCC) on a horse's genitalia, what clinical scenario warrants strong consideration of euthanasia?
What is the MOST significant difference between equine melanoma and sarcoids regarding tumor behavior and origin?
What is the MOST significant difference between equine melanoma and sarcoids regarding tumor behavior and origin?
Why are draft horse breeds particularly predisposed to chronic progressive lymphedema (CPL)?
Why are draft horse breeds particularly predisposed to chronic progressive lymphedema (CPL)?
What is the BEST long-term management approach for horses diagnosed with Chronic Progressive Lymphedema (CPL)?
What is the BEST long-term management approach for horses diagnosed with Chronic Progressive Lymphedema (CPL)?
In cases of suspected ulcerative lymphangitis (caused by Corynebacterium pseudotuberculosis), what initial diagnostic tests are MOST crucial to confirm the diagnosis and guide treatment?
In cases of suspected ulcerative lymphangitis (caused by Corynebacterium pseudotuberculosis), what initial diagnostic tests are MOST crucial to confirm the diagnosis and guide treatment?
Flashcards
Pruritus
Pruritus
Itching, a common dermatological complaint.
Scaling and Crusting
Scaling and Crusting
Skin lesions marked by scales and crusts.
Nodular Lesions
Nodular Lesions
Solid, raised skin lesions greater than 1 cm.
Neoplasia
Neoplasia
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Pigment Disorders
Pigment Disorders
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Parasitic Skin Diseases
Parasitic Skin Diseases
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Dermatophytosis
Dermatophytosis
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Dermatophilosis
Dermatophilosis
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Pediculosis
Pediculosis
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Acariasis
Acariasis
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Culicoides Hypersensitivity
Culicoides Hypersensitivity
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Onchocerciasis
Onchocerciasis
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Atopy
Atopy
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Ulcerative Lymphangitis
Ulcerative Lymphangitis
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Sporotrichosis
Sporotrichosis
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Habronemiasis
Habronemiasis
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Pythiosis
Pythiosis
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Sarcoid
Sarcoid
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Squamous Cell Carcinoma
Squamous Cell Carcinoma
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Melanoma
Melanoma
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Vitiligo
Vitiligo
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Leukoderma
Leukoderma
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Reticulated Leukotrichia
Reticulated Leukotrichia
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Fistulous Withers
Fistulous Withers
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HERDA
HERDA
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Pemphigus Foliaceus
Pemphigus Foliaceus
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Study Notes
Equine Dermatology: Objectives
- Focus on pruritic, scaling and crusting, nodular, neoplastic, and pigment disorders
- Key plans to form a list of differential diagnoses (DDx) for each disorder, a diagnostic plan, and a therapeutic plan
Parasitic Skin Diseases and Key Differentials
- Study external and internal parasitic skin diseases affecting horses
- Consider the lifecycle, clinical signs, diagnosis, and treatment of each
- Grasp the differences between ringworm (dermatophytosis) and rainscald (dermatophilosis)
Differentials and Equine Sarcoids
- Comprehend differentials for nodular lesions, including neoplasms and infections
- Assess the prognosis for each differential
- Review treatment options for equine sarcoids
Dermatology in Practice
- Dermatology problems are commonly seen in practice
- Diagnosis can often be made initially based on physical exam and history
- Many cases improve or resolve with treatment
- Some cases necessitate more diagnostic tests
Evaluation of the Equine Dermatology Patient
- A thorough history is vital
- Conduct a comprehensive physical examination
- Utilize appropriate diagnostic testing
History: Duration and Progression
- Determine how long the condition has been present
- Understand how the condition has progressed over time; it can be as short as four days, to as long as six months
History: Seasonality
- Note when the problem occurs
- Determine if the condition is associated with insects
History: Herd vs. Individual Animal
- Assess whether the condition affects a single animal or multiple animals within a herd
History: Zoonotic Evidence
- Check if the owner or caretaker exhibits similar lesions, which could indicate a zoonotic disease
History: Treatments Tried
- Inquire about previous treatments
- Consider that some treatments might obscure the original condition or even create more lesions
Physical Exam: Lesion Characteristics
- Evaluate the type and configuration of lesions, such as pustules, crusting, and ulcerations
- Determine if the lesions are pruritic or nonpruritic
- Note if lesions are raised, dermal, subcutaneous, or annular
- Record lesion distribution including dorsal, ventral, limbs, head, mane and tail
- Note any cutaneous manifestations of systemic disease
Diagnostic Testing: Skin Scraping
- Use mineral oil and a #22 blade to scrape the edge of new lesions
- This technique can help in identifying mites and mange
Diagnostic Testing: Culture Samples
- Collect culture samples by taking hairs or performing a biopsy
- Bacterial and fungal cultures should be taken
Diagnostic Testing: Skin Biopsy
- Avoid prepping the skin before the biopsy
- Biopsies can help diagnose immune-mediated, allergic, larval, and neoplastic conditions
Diagnostic Testing: Minced Preparation
- This is used to detect larval migration
Diagnostic Testing: External Parasites
- Simply examine the horse for external parasites
- Consider that some external parasites can fly, while others cannot
Outline of Dermatology Diseases
- Pruritic Skin Diseases
- Scaling/Crusting Diseases
- Nodular Skin Diseases
- Dermal Neoplasia
- Disorders of Pigmentation
- Miscellaneous
Pruritic Skin Diseases
- Include ecto- and endoparasites
- Allergic or hypersensitivity reactions
- Secondary bacterial infections
- Pruritic conditions aren't typically primary infectious issues, however, there are exceptions
Wilma: A Case of Pruritus
- Wilma is a 25-year-old Draft horse suffering from severe pruritus and hair loss, worsening in winter
Pediculosis: Lice Infestation
- Lice are the most common ectoparasite in horses
- These are host-specific
- Lice infestation is seasonal, typically occurring in winter when nits hatch
- Sucking lice (Haematopinus asini) infest the mane and tail, feeding on blood
- Biting lice (Damalinia equi) are found on the dorsolateral trunk, consuming epidermal debris
- Lice infestations cause a patchy, rough haircoat, pruritus, alopecia, and debilitation
- Diagnosis is typically done via visual inspection
Lice Transmission
- There is little to no zoonotic potential
- Lice complete their entire life cycle on the host
- Lice survive for only days to weeks in the environment
- Transmission can occur via contaminated tack, bedding, and brushes
- Asymptomatic adults can act as reservoirs
Lice Treatment
- Ivermectin or moxidectin treats sucking lice
- Topical pyrethrin needs to be repeated
- Disinfect tack, brushes, blankets, and premises with commercial premise flea spray
- Fipronil has evidence in other species
7-Year-Old Draft Gelding: A Case for Consideration
- A 7-year-old Draft Gelding presents with an intense pruritic lesion on the lower leg
Acariasis: Mange
- Mange is characterized by intense pruritus, crusting, and exudation
- A skin scrape is a good solution
- Chorioptic mange is common in Draft horses, typically affecting the legs (Chorioptes equi)
- Trombicula, or chiggers, can also cause mange
- Sarcoptic mange affects the head and neck and is reportable (Sarcoptes scabiei var equi)
- Psoroptic mange affects the mane and tail area and is reportable (Psoroptes equi)
Chorioptic Mange
- Draft horses are predisposed to chorioptic mange, which typically affects their legs
Treatment of Mange
- Clip hair from the feathers and pastern to improve access for treatment
- Use ivermectin or moxidectin
- Topical pyrethrin needs to be repeated
- Lime sulfur dips must be repeated as well
- Decontaminate premises, brushes, and tack with parasiticidal flea products
- Frontline is another treatment
Ticks
- Ticks transmit diseases
- They can cause urticaria and secondary bacterial infections
- The most common locations found include ears, perineum, axilla, distal limbs, mane, and tail
- Frontline is an effective treatment for legs, mane, and tail
Onchocerciasis
- Adult nematodes reside in the nuchal ligament
- Microfilariae are found subcutaneously in the ventral midline
- Transmitted through Culicoides
Onchocerciasis: Clinical Signs
- Includes alopecia, ulceration, and lichenification
- Common areas affected are the head and ventral midline
- It is seasonal
- Rare in horses less than 3-4 years old
Onchocerca Diagnosis
- Skin scrapings are negative
- Histopathology reveals eosinophilic perivascular cuffing
- Minced skin preparations will show microfilaria
Onchocerciasis Treatment
- Ivermectin and moxidectin treat microfilaria
- Steroids like prednisolone and dexamethasone may be needed
Flying & Biting Insects: Significant Problem
- Some insects that are a problem include midges (Culicoides), black flies (Simulian), horn flies (Hematobia), deer and horse flies, stable flies, and mosquitos
Culicoides Hypersensitivity
- It's also known as Queensland itch or sweet itch
- Seasonal, occurring from spring through summer
- Results in pruritic dermatitis, alopecia, crusts, and scaling
- It results in self-trauma and damage to barn/fencing
- Distribution is typically on the mane, tail, and pectoral region
- Type I hypersensitivity, therefore, is heritable
Culicoides Characteristics
- Known as "no-see-ums"
- They are biting midges that are small in size
- Culicoides typically feed at dusk and dawn
Diagnosing Insect Hypersensitivity
- History and clinical signs are most important
- Note the season, environment, and distribution of lesions
- Note that a skin scrape is not helpful
- Note that skin biopsy shows eosinophilic dermatitis
- It is not specific for hypersensitivity
- It is used to rule out other diseases
Insect Hypersensitivity: Treatment
- Prevent exposure by bringing in the horse at night, if the insect is culicoides
- Bring in the horse during the day (shade, fans), if the insect is a stable, horse & deer fly
- Fly traps can be useful
- Use small-mesh screens or netting (32 x 32)
- Insecticides including mist sprayers (pyrethrins)
- And Permethrin (44%-64%)
Insect Hypersensitivity: Immediate Relief
- Use steroids like dexamethasone and prednisolone
- Use antihistamines such as hydroxyzine
Insect Hypersensitivity & Atopy
- Atopy is a genetically programmed disease where the patient becomes sensitized to an environmental antigen
- Atopy is more common in young horses less than 4 years old
- Atopy is more likely to respond in hyposensitization
Pruritus: Miscellaneous Etiologies
- Food allergies to potatoes, malt, beet pulp, alfalfa can cause GI, skin, and respiratory consequences
- Contact allergy
- Contact irritant
- Cutaneous drug reaction with Penicillin or sulfa-based antimicrobials
Tail Rubbing: Pinworms
- Pinworms are getting more common
- There are some concerns with resistance
- Dx: Fecal (tongue depressor or tape)
- Rx: Most anthelmintics
Tail Rubbing: Iatrogenic Causes
- Western show horses can have painful pruritus
- Alcohol at the base of the tail is unethical medical procedure
Scaling and Crusting
- Dermatophilosis (rain scald)
- Dermatophytosis
- Bacterial infection (Staphylococcus)
- Autoimmune conditions
- Severe pruritus causing trauma
- Photosensitization on while areas
- Pastern Dermatitis
Dermatophilosis
- Also known as Dermatophilus congolensis
- Rain scald and rain rot is caused by moisture and maceration
- It is a gram-positive, facultative anaerobic actinomycete (bacteria)
- It has a season predilection of winter and spring
- It forms crusted, moist, mats of hair or paintbrushes
- Skin is ulcerated, moist, and yellow to pink
- Distribution is dorsal, on the limbs, and muzzle
- Carrier animals are a reservoir of infection
Diagnosis: Rain Scald
- Impression smear reveals double rows of cocci in a "railroad tract"
- Bacterial culture should be performed
- Histopathology is used to visualize organisms on skin crust
Treatment: Rain Scald
- Bathe with chlorhexidine
- Sedation may be required
- Use systemic antibiotics for severe cases
- Eliminate predisposing factors
Ringworm
- Ringworm is caused by Trichophyton equinum*, metagrophytes, or verrucosum, or Microsporum gypseum and equinum
- It is most common contagious skin disease of horses
- It is acquired by direct contact and exposure to infected fomites
- It is worsened by debilitation, moisture, and stress
- Horses get alopecia and crust papules
- It is characyerized by circumferential spread (bulls-eye lesion)
Diagnosis: Ring Worm
- Wood's lamp is rarely successful
- Skin scrapes are rarely successful
- Fungal culture is a great solution
- Histopathology is used to identify septate hyphae or oval spores in superficial keratin or hair follicle
Treatment: Ringworm
- Self-limiting in 1 to 6 months
- Contagious and zoonotic potential
- Systemic antifungal medications are expensive and unnecessary
- Anti-fungal shampoos/topical treatments
Duke: A Case Study
- Duke is an 18 year old QH gelding
- Showing Crusting, Occasional pustules, Ventral Edema
- Initially Responded to Dexamethasone
Duke's Likely Diagnosis
- Phemigus is likely
- Consider other potential cases like ringworm due to immunosuppression, bacterial skin infection, and sunburn
Pemphigus Foliaceus
- Autoimmune skin disease (Type II hypersensitivity)
- Antibody against intercellular cement
- Non-pruritic (usually)
- Exhibits crusting, alopecia, matting of hair, subcorneal pustules
- Begins on head and spreads to the entire body
Diagnosing Pemphigus
- Histopathology is key, revealing subcorneal acantholysis and neutrophilic inflammation
- Direct immunofluorescence confirms intercellular cement
Pemphigus Foliaceus: Prognosis
- Less than on year of age - Excellent prognosis for cure with steroids
- Adults - unrewarding, chronic therapy with Steroids is the solution, however, may be non-responsive or problems associated with use
Distal Limb Dermatitis
- Pastern folliculitis caused by Staph spp, Dermatophilus or Chorioptes
- Scratches
- Dew Poisoning
- Mud Fever
- Greasy Heel
Distal Limb Dermatitis: Management
- Consider Biopsy & Culture
- Change conditions
- Bandage
- NSAID
- Antibiotics..
Chronic Progressive Lymphedema in Draft Horses
- Can be found in Shires, Clydesdales, Belgian, Gypsy Varner, English Cobbs, German Draft, Friesian, and Percheron (Europe) horses
Altered Elastin Metabolism
- It is paired with impaired lymphatic functions
- Primary lymph edema in humans
- Elephantiasis verrucosa nostra
- Genetics likely play a role
- 2nd infections occur such as Bacterial & Chorioptes
Management of Chronic Progressive Lymphedema
- It is a lifelong disease
- Treat bacterial & parasitic diseases
- Implement daily skin care with clipping feathers, washing and dry, daily exercise, and maintaining a clean environment
Combined Decongestive Therapy
- Treatment includes Humans
- With Manual lymph drainage
- Compression bandages
- Specialized short-stretch bandages
What is this?
- Photosensitization
Photosensitization Causes
- Primary: Plant derived, from St. John's Wort for example
- Secondary: Liver related; the performance profile has Plants also associated with liver disease
Nodular Skin Diseases
- Nodular is ulcerated and non-ulcerated
- Hives
- Neoplasia
- Proud Flesh
- Parasitic
- Bacterial
- Fungal Infections
Diagnoses: 6-year-oldTB with Pruritic Lesions
- Differential Diagnoses or Treatment?
Hives: Type I Hypersensitivity
- What is my horse allergic to?
- Skin Testing is a potential diagnostic
- Blood Tests, not well correlated to skin testing, are another
- Treatment is Dexamethasone or.. Flunixin meglumine
Lump on Back
- Hard
- Non-pruritic & nonpainful
- The is an Eosinophilic granuloma
Nodular Necrobiosis
- Eosinophilic granulomas Etiology unknown
- Single or multiple, haired, raised, firm dermal masses 0.5 to 10 mm in diameter
- Nonpainful and non-pruritic
- Located on the Neck, withers, and dorsal trunk
Nodular Necrobiosis Diagnosis
- Skin biopsy shows collagen degeneration with eosinophilic inflammation.
- Intralesional triamcinolone is a solution (not to exceed 20 mg).
Papillomatosis
- Caused by Papilloma virus, commonly seen in young horses, 12 to 24 months of age
- Commonly forms Distribution: muzzle, eye, ear
- Diagnosis: visual inspection
Papillomatosis: Treatments
- Benign neglect approach
- Crush lesions to release antigens
- Immunostimulant therapy, like EqStim
Diseases With These Traits
- Multiple, Raised, Dermal, Non-Haired, Nonpainful, Nonpruritic
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