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🐾 CANINE DISTEMPER DISEASE (CDV) — Complete Veterinary Guide

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PART 1 — THE VIRUS ITSELF (Etiology)

What Causes It?

• Family: Paramyxoviridae
• Genus: Morbillivirus
• Type: Single-stranded, negative-sense RNA virus (enveloped)
• Shape: Pleomorphic (not always a fixed shape) — roughly spherical
• Size: 150–250 nm in diameter

• Human Measles Virus (HMV)
• Rinderpest Virus of cattle

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Viral Structure — Know the Proteins

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Viral Lineages

• 17 official lineages have been described worldwide
• An 18th lineage was proposed in India (2019)
• Genetic variation is highest in the H protein gene
• This variation creates challenges for vaccines because old vaccine strains may not perfectly neutralize newer wild strains

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PART 2 — EPIDEMIOLOGY

Who Gets It?

• Domestic dogs (most common)
• Wild dogs, wolves, coyotes, foxes, jackals

• Ferrets (extremely susceptible — often fatal)
• Minks, otters, badgers, wolverines

• Raccoons

• Lions, leopards, tigers, cheetahs — CDV outbreaks have caused mass mortalities in wild lion populations (Serengeti, Tanzania)

• Recent emergence in non-human primates in Brazil (2025 — Santos et al. [PMID: 41287151])

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How Does It Spread? (Transmission)

• Primary route: Direct contact — inhalation of aerosolized respiratory secretions (sneezing, coughing)
• Secondary routes: Contact with infected urine, feces, ocular/nasal discharge
• Virus in environment: CDV is unstable — it dies quickly in the environment at room temperature. However, it survives longer in cold temperatures (below 4°C)
• No insect vectors — only direct animal contact
• Vertical transmission possible: infected pregnant females can pass CDV to puppies (stillbirths, abortions)

• Unvaccinated puppies aged 3–6 months (after maternal antibody wanes)
• Immunocompromised dogs
• Shelter dogs with poor vaccination coverage

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PART 3 — PATHOGENESIS (How CDV Destroys the Body)

Step 1 — Entry and Initial Replication (Days 1–4)

• CDV enters via the respiratory tract (inhaled aerosols)
• The virus uses two main receptors to enter cells:
  • SLAM (Signaling Lymphocyte Activation Molecule) — expressed on immune cells (lymphocytes, macrophages, dendritic cells)
  • Nectin-4 — expressed on epithelial cells of respiratory and GI tracts
• The virus first infects macrophages and dendritic cells in the tonsils and bronchial lymph nodes
• Initial replication = rapid viral multiplication in lymphoid tissue

Step 2 — Primary Viremia (Days 4–6)

• CDV spreads through the bloodstream (inside lymphocytes and monocytes) to all lymphoid organs:
  • Spleen, thymus, lymph nodes, bone marrow, Peyer's patches in the gut
• Severe lymphopenia develops — the virus destroys T and B lymphocytes
• This creates profound immunosuppression — the dog cannot fight CDV or any secondary infection
• Clinical sign at this stage: high fever (40–41°C), lethargy, anorexia

Step 3 — Secondary Viremia (Days 7–14)

• If the dog cannot mount a strong antibody response, the virus escapes lymphoid tissue
• CDV spreads to epithelial cells throughout the body via Nectin-4:
  • Respiratory tract (bronchi, lungs)
  • Gastrointestinal tract
  • Urogenital tract
  • Skin
  • Uvea of the eye
  • Central nervous system

Step 4 — Organ Involvement

• Directly through the olfactory nerve
• Via infected lymphocytes crossing the blood-brain barrier

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The Three Patterns of CDV in the Nervous System

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PART 4 — CLINICAL SIGNS (What You See on Exam)

Phase 1 — Early/Systemic Signs (first 1–2 weeks)

• Biphasic fever — first spike at day 3–6, then returns
• Lethargy and depression
• Loss of appetite (anorexia)
• Serous (watery) nasal discharge → becomes mucopurulent (thick, green-yellow)
• Serous then mucopurulent ocular discharge
• Mild cough
• Lymphopenia on blood work

Phase 2 — Respiratory Signs

• Dry cough → productive moist cough
• Rhinitis, sinusitis
• Bronchopneumonia — crackling lung sounds on auscultation
• Dyspnea (difficulty breathing) in severe cases
• Lung consolidation visible on X-ray

Phase 3 — Gastrointestinal Signs

• Vomiting
• Hemorrhagic or profuse diarrhea
• Dehydration
• Mucous bloody stool in severe cases

Phase 4 — Neurological Signs (can appear weeks to months later)

• Myoclonus (chewing gum seizures) — rhythmic twitching of jaw or limbs — this is PATHOGNOMONIC (unique) for CDV
• Focal or generalized seizures
• Ataxia (wobbly gait, falling)
• Paresis or paralysis (limb weakness)
• Head tilt, circling
• Nystagmus (rapid eye movements)
• Hyperesthesia (increased sensitivity to touch)
• Mental dullness, behavior changes
• Vestibular signs (balance problems)

Clinical pearl: Neurological signs can appear in dogs that seemed to recover from the respiratory phase — this is called "late neurological distemper."

Phase 5 — Other Organ Signs

• Keratoconjunctivitis sicca (dry eye) — CDV destroys the lacrimal gland
• Anterior uveitis (red, painful eye)
• Optic neuritis — sudden blindness
• Chorioretinitis — white/gray lesions visible in the retina on fundoscopy

• Hyperkeratosis of footpads — pads become hard, cracked, dry → this is called "Hard Pad Disease" (old name for CDV)
• Hyperkeratosis of the nose (planum nasale)

• Enamel hypoplasia — permanently pitted, discolored teeth if puppy was infected during tooth development

• Pregnant females: abortion, stillbirths, weak "fading" puppies

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PART 5 — GROSS PATHOLOGY & HISTOPATHOLOGY (What You See at Necropsy)

Gross (macroscopic) Lesions:

• Thymic atrophy — shrunken, pale thymus (especially in puppies)
• Lung consolidation — gray-red firm patches
• Splenomegaly in some cases
• Mucosal erosions in GI tract
• Hard, cracked footpads
• Demyelinating white matter lesions visible in brain cross-sections

Histopathology (Microscopic) Lesions:

• Intranuclear and intracytoplasmic inclusion bodies in epithelial and neuronal cells — CLASSIC finding
  • Lentz inclusion bodies — eosinophilic (pink-staining) inclusions
• Interstitial pneumonia with alveolar infiltration by lymphocytes and macrophages
• Demyelination with gliosis — loss of myelin sheaths in the white matter of the brain and spinal cord
• Perivascular lymphocytic cuffing — cuffs of lymphocytes around blood vessels in the brain
• Meningoencephalitis
• Lymphoid depletion in spleen, thymus, lymph nodes

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PART 6 — DIAGNOSIS

Step 1 — Clinical Suspicion

• Multisystemic signs (respiratory + GI + neurological together)
• Mucopurulent ocular/nasal discharge
• Hard footpads
• Myoclonus (jaw twitching)

Step 2 — Laboratory Testing

Blood Work (CBC + Chemistry)

• Lymphopenia — hallmark finding
• Neutrophilia (if secondary bacterial infection)
• Thrombocytopenia in some cases
• Elevated liver enzymes possible
• Hypoalbuminemia (protein loss through GI)

Specific CDV Tests

Best Samples to Submit:

• Live dog: Conjunctival swab + urine + blood (EDTA) → RT-PCR
• Neurological dog: CSF + blood → RT-PCR
• Dead animal: Tonsil, spleen, lung, brain tissue → IHC + histopathology + FA

Key point: IFA on tissue becomes negative once the dog develops antibodies or if only neurological signs are present. In those cases, CSF RT-PCR is your best tool.

Differential Diagnosis (What Else Could It Be?)

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PART 7 — TREATMENT

1. Keep the dog alive while the immune system fights the virus
2. Control secondary infections
3. Manage neurological and GI signs

Supportive Care

• IV crystalloids (Normal Saline, Lactated Ringer's Solution)
• Correct dehydration, electrolyte imbalances
• Maintain blood pressure
• Rate: based on dehydration percentage + maintenance needs

• Assist feeding if not eating — syringe feeding or nasogastric tube
• High-quality, easily digestible food
• Dogs with GI signs: bland diet (chicken + rice), small frequent meals

• Not to kill CDV (virus is unaffected by antibiotics)
• Target: secondary bacterial pneumonia, urinary tract infections
• Common choices:
  • Amoxicillin-Clavulanate (Clavamox)
  • Enrofloxacin
  • Doxycycline (also anti-inflammatory effects in respiratory tissue)
  • Chloramphenicol (CNS penetration if neuro signs)
• Duration: 7–14 days minimum

• Nebulization with saline ± bronchodilators (Albuterol)
• N-Acetylcysteine (mucolytic) for thick secretions
• Coupage (physiotherapy chest tapping) to mobilize secretions
• Oxygen therapy for dogs with pneumonia (SpO₂ < 94%)

• Anti-emetics: Maropitant (Cerenia), Metoclopramide
• Anti-diarrheal: Metronidazole (also anti-inflammatory)
• GI protectants: Omeprazole, Sucralfate
• Probiotics: help restore normal gut flora

• Phenobarbital — anticonvulsant for seizures (2–5 mg/kg PO BID)
• Potassium bromide — add-on if seizures not controlled
• Diazepam (IV) — for acute status epilepticus
• Methocarbamol — muscle relaxant for severe myoclonus
• For brain edema: Dexamethasone (short-term; controversial due to immunosuppression)

• Artificial tears for keratoconjunctivitis sicca (KCS)
• Antibiotic eye drops (Chloramphenicol, Tobramycin) for secondary bacterial conjunctivitis
• Atropine eye drops for anterior uveitis

• Vitamin A — supports epithelial integrity and immune response
• Vitamin C — antioxidant support
• Vitamin B complex — neurological support

• Ribavirin — shows in vitro activity against CDV, but toxic in dogs (hemolytic anemia, bone marrow suppression). Not routinely used.
• Immunomodulators — Interferon-α (human or feline recombinant): some clinical reports of benefit, especially for neurological CDV. NOT proven in controlled trials.

Isolation Protocol

• ALL suspected CDV cases must be immediately isolated from other dogs
• Barrier nursing: gloves, gown, separate equipment
• CDV is killed by most common disinfectants: bleach (1:32), Virkon, quaternary ammonium compounds
• Virus dies at 50–60°C in minutes

Prognosis

• Dogs that develop myoclonus rarely recover fully — the myoclonus often remains permanent even after the infection resolves
• Overall mortality rate: 50% in dogs showing neurological signs
• Surviving dogs may have permanent neurological deficits, dry eyes, or enamel hypoplasia

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PART 8 — PREVENTION & VACCINATION

Core Vaccine — DHPP / DA2PP

Vaccination Schedule

• First vaccine: 6–8 weeks of age
• Booster: every 3–4 weeks until 16 weeks old (minimum 3 doses)
• Why? — Maternal antibodies (from mother's colostrum) block the vaccine until they wane
• Final puppy dose should be at or after 16 weeks to ensure protection

• Booster: 1 year after last puppy dose
• Then every 3 years (per WSAVA guidelines for MLV vaccines)

• Modified Live Virus (MLV) — most common, most effective. Provides faster and stronger immunity. Risk of post-vaccinal encephalitis is extremely rare but documented.
• Recombinant canary pox-vectored vaccine (e.g., Recombitek) — safer for immunocompromised dogs and wildlife
• Inactivated (killed) vaccines — used less often; require adjuvant; weaker immunity; multiple doses needed
• MLV Measles vaccine — historically used to protect puppies that still have maternal antibodies to CDV; measles virus is antigenically related enough to cross-protect

Vaccine Failure — Why It Happens?

• Vaccination during the "window of susceptibility" when maternal antibodies are too high to allow response but too low to protect
• Inadequate cold chain (vaccine not kept at 2–8°C)
• Dog already infected at time of vaccination
• Antigenic mismatch — increasing concern because wild CDV strains (especially in Asia, Europe, South America) differ significantly from classic Snyder Hill or Lederle vaccine strains in the H protein

Wildlife Control

• In shelters: vaccinate ALL dogs immediately upon intake + booster in 14 days
• Oral bait vaccines are being developed/tested for wild carnivores
• Wildlife populations (lions, wild dogs) remain at high risk because no practical mass vaccination program exists for them

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PART 9 — PRE-SURGICAL ASSESSMENT & POST-SURGICAL CARE IN VETERINARY MEDICINE

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SECTION A — PRE-SURGICAL (Before Surgery)

1. Patient History (Anamnesis)

• Signalment — species, breed, age, sex, weight
• Chief complaint — why is surgery needed?
• Vaccination history — is the dog current on vaccines?
• Medication history — any current drugs? (NSAIDs, anticoagulants, steroids — these affect surgery)
• Previous surgeries — any anesthetic reactions?
• Allergies — to drugs, materials
• Last meal — fasting status
• Reproductive status — intact female? Could be pregnant?
• Diet history, travel history, recent illness

2. Physical Examination (Pre-Op PE)

3. ASA Physical Status Classification (Risk Scoring)

4. Pre-Operative Diagnostic Tests

• CBC (Complete Blood Count): Check for anemia, infection, thrombocytopenia
• Serum Chemistry Panel: Liver (ALT, ALP), kidneys (BUN, creatinine), glucose, electrolytes
• Urinalysis: Kidney function, UTI
• PCV (Packed Cell Volume) + Total Protein: Quick anemia/protein check

• Clotting times (PT, aPTT): If bleeding disorder suspected, or on anticoagulants
• Thoracic X-rays: Lung disease, cardiac size, metastasis check
• Abdominal ultrasound: Organ masses, free fluid
• ECG: Dogs >7 years, or known cardiac disease
• Blood pressure: Hypertensive patients
• Blood type + crossmatch: If major blood loss expected (surgery for splenic rupture, etc.)

5. Fasting (NPO — Nothing by Mouth)

• Food: Withhold for 8–12 hours before surgery
• Water: Can be given up until 2–4 hours before, then withheld
• Purpose: Prevent aspiration of stomach contents under anesthesia (aspiration pneumonia = deadly complication)
• Caution: Neonates and diabetics should NOT be fasted as long — risk of hypoglycemia

6. Pre-Anesthetic Medications (Premedication)

7. IV Catheter Placement

• Place an IV catheter in the cephalic or saphenous vein before induction
• Allows: drug delivery, fluid therapy, emergency drug access

8. Anesthesia Induction

• Propofol IV — most common induction agent in dogs; smooth and controllable
• Alfaxalone — alternative; useful in compromised patients
• After induction: intubate the trachea with an endotracheal tube to:
  • Protect airway from aspiration
  • Deliver inhalant anesthesia (Isoflurane or Sevoflurane)

9. Intraoperative Monitoring

• Heart rate and rhythm (ECG)
• SpO₂ (pulse oximetry) — keep > 95%
• Blood pressure (BP) — keep mean arterial pressure > 60 mmHg
• End-tidal CO₂ (ETCO₂) — keep 35–45 mmHg
• Temperature — keep > 37°C; use warm IV fluids, warming blanket
• Depth of anesthesia — response to stimulus, eye position, jaw tone
• IV fluid rate — maintenance: 5–10 mL/kg/hr during surgery

10. Surgical Site Preparation

• Clip hair widely around the surgical site (at least 5 cm margin)
• Clean with chlorhexidine or povidone-iodine scrub → alternating with sterile saline/alcohol
• Minimum 3 scrub cycles using a spiral-outward motion
• Apply sterile drapes around the surgical field

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SECTION B — TYPES OF VETERINARY SURGERY

• Spay (ovariohysterectomy) and neuter (orchiectomy/castration)
• Lump/mass removal (skin tumors, lipomas)
• GI surgery: foreign body removal, enterotomy, intestinal resection & anastomosis
• Bladder surgery (cystotomy for stones)
• Gastric dilatation-volvulus (GDV) decompression and gastropexy
• Liver/spleen surgery
• Lung lobectomy
• Wound repair and skin grafts
• Hernia repair

• Fracture repair (plates, screws, pins, external fixators)
• TPLO (Tibial Plateau Leveling Osteotomy) for cruciate ligament rupture
• Luxating patella repair
• Femoral head and neck excision (FHO)
• Arthroscopy

• Cherry eye correction
• Enucleation (eye removal)
• Cataract surgery

• Disc surgery (hemilaminectomy for IVDD)

• Tooth extractions, jaw fracture repair

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SECTION C — POST-SURGICAL CARE

1. Recovery Room (Immediate Post-Op — First 1–2 Hours)

• Keep in a quiet, warm, padded area
• Monitor continuously — do not leave alone until fully awake
• Keep in sternal recumbency (chest down, not flat on side) — reduces aspiration risk
• Extubate (remove endotracheal tube) when dog shows swallowing reflexes
• Monitor vital signs every 15 minutes:
  • Temperature (hypothermia is common post-op — keep warm)
  • Heart rate and rhythm
  • Respiratory rate
  • Blood pressure
  • SpO₂
  • Pain score (see below)
• Keep IV catheter in place until dog is stable and alert
• Continue IV fluids until drinking on its own

2. Pain Assessment (Critical Post-Op Skill)

• Glasgow Composite Pain Scale (GCPS) — behavioral indicators
• Colorado State University Acute Pain Scale — visual scale

• Vocalization (whimpering, crying)
• Restlessness, inability to settle
• Hunched posture, guarding the surgical site
• Biting or licking the incision
• Dilated pupils, elevated heart rate
• Aggression when touched near incision

3. Post-Operative Analgesia

4. Wound Care & Incision Monitoring

• Elizabethan collar (E-collar / cone of shame) — must be worn at all times to prevent licking and biting
• Bandaging — especially for orthopedic limb wounds
• Keep incision dry — no bathing until sutures are removed (10–14 days)
• No swimming, no running

5. Activity Restriction

• Strict rest for 10–14 days minimum for soft tissue surgery
• 4–8 weeks for orthopedic surgery
• Short leash walks only for urination/defecation
• No jumping, stairs, rough play
• Baby gates or crate rest to restrict movement

6. Post-Op Medications Typically Prescribed

7. Feeding Post-Surgery

• Withhold food for 2–4 hours after recovery (nausea from anesthesia)
• Offer small amounts of water first
• Gradual return to normal food over 24 hours
• For GI surgery: special liquid diet or easily digestible food for 5–7 days

8. Suture/Staple Removal

• Skin sutures/staples removed at 10–14 days
• Internal (absorbable) sutures dissolve on their own
• At suture removal: reassess wound for complete healing

9. Follow-Up Visits

• 1–3 days post-op: pain check, wound check
• 10–14 days: suture removal
• 4–6 weeks: recheck for orthopedic surgery, healing assessment
• 6–8 weeks: full return to normal activity for major surgery

10. Red Flags — When to Return to the Vet Immediately

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QUICK SUMMARY CARDS

CDV — Key Facts for Exams

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• Jawetz, Melnick & Adelberg's Medical Microbiology 28e (Paramyxoviruses chapter)
• Merck Veterinary Manual — Canine Distemper
• Karki M et al. — Canine morbillivirus (CDV): a review on current status, emergence and diagnostics. Virusdisease 2022 [PMID: 36039286]
• Rivera-Martínez A et al. — Canine Distemper Virus: Origins, Mutations, Diagnosis, and Epidemiology in Mexico. Life 2024 [PMID: 39202744]
• Rendon-Marin S et al. — Safety and Immunogenicity of CDV Vaccines. Viruses 2024 [PMID: 39066240]
• AAHA Anesthesia and Monitoring Guidelines for Dogs and Cats 2020
• VCA Animal Hospitals — Pre-surgical Preparation and Testing
• Preoperative Planning — Veterian Key (veterinary surgery textbook source)

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🐾 CANINE HERPESVIRUS DISEASE (CHV-1) — Complete Veterinary Guide

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PART 1 — THE VIRUS ITSELF (Etiology)

What Causes It?

• Canid Herpesvirus 1 (CaHV-1)
• Varicellovirus canidalpha1 (new official name)

Why Is It Called an Alphaherpesvirus?

1. Fast replication in host cells
2. Wide host cell range — can infect many different cell types
3. Establish latency in nerve ganglia (they hide in the nervous system and never fully leave)

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Viral Structure — Know the Proteins

1. Core — contains the linear dsDNA genome
2. Icosahedral Capsid — protein shell surrounding the genome
3. Tegument — amorphous protein layer between capsid and envelope; contains viral proteins that help take over the host cell immediately after entry
4. Envelope — lipid bilayer (taken from the host cell membrane) studded with glycoproteins

• gB — cell entry (membrane fusion)
• gC — cell attachment to heparan sulfate on host cell surface
• gD — binds specific host entry receptors
• gE and gI — help the virus spread cell-to-cell without being detected by antibodies

• Common disinfectants (bleach, alcohol, iodine, Virkon)
• Detergents and soaps
• Heat above 37°C (very important — this is why temperature management saves neonates)
• Drying (the virus does not survive long outside the host)

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Key Biological Property — Temperature Sensitivity

CHV-1 replicates optimally at 35–36°C (95–97°F)

• Normal adult dog body temperature: 38.5–39.2°C
• This temperature is too high for CHV-1 to replicate effectively — so adult dogs control the infection
• Neonatal puppies CANNOT regulate their own body temperature. Their core body temperature is often 35–36°C — the PERFECT temperature for CHV-1 to multiply
• This is why neonates die and adults survive

• Why only neonates die
• Why warming incubators save puppies
• Why the upper respiratory tract (cooler mucous membranes) and genital tract are the main sites in adults

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PART 2 — EPIDEMIOLOGY

Who Is Affected?

• Domestic dogs — primary and most important host
• Wild canids — wolves, foxes, coyotes, jackals
• Does NOT infect humans, cats, or most other species — host range is restricted to canids

Global Distribution

• In kennels and breeding facilities: 30–100% of dogs — most studies report ~80% seropositive in kennel populations
• In random pet dog populations: 40%+ in European studies; <10% in some US random studies
• The true prevalence is likely underestimated because:
  • Antibody titers drop rapidly after infection (within 1–2 months)
  • Many infections are subclinical
  • Testing is not always done

Who Is Most at Risk?

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PART 3 — TRANSMISSION

How Does CHV-1 Spread?

• Nasal secretions, oral secretions (sniffing, licking, playing)
• Vaginal/preputial secretions (sexual contact, genital licking)
• Urine

• When a puppy passes through an infected birth canal, it is directly exposed to high concentrations of CHV-1 in vaginal secretions
• This is the most common route of infection in neonates

• During acute primary CHV-1 infection in a pregnant bitch
• Virus crosses the placenta and infects the fetuses directly
• Results in: fetal death, abortion, mummification, stillbirth, or premature birth of weak/infected puppies

• Inhalation of infectious aerosols from infected dogs
• Responsible for mild upper respiratory infections in adult dogs

• Via contaminated hands, fomites (equipment, bedding) — but CHV-1 is fragile in the environment, so this is less important than direct contact

• Latently infected adult dogs periodically reactivate and shed virus — often without any visible symptoms
• Triggers for reactivation:
  • Stress (transport, surgery, new environment)
  • Corticosteroid/immunosuppressive drug administration
  • Pregnancy and whelping — the hormonal changes around parturition can reactivate CHV-1 in the mother, exposing her own newborn puppies

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PART 4 — PATHOGENESIS (Step by Step)

In Neonatal Puppies (< 3 weeks)

• Virus enters via the oronasal route (licking the infected mother's mouth/nose), respiratory tract, or during passage through the infected birth canal
• Initial replication in the tonsils and upper respiratory mucosa

• Because the puppy's body temperature (35–36°C) is ideal for CHV-1, the virus replicates explosively
• Virus spreads via the bloodstream to ALL major organs within 24–48 hours

• CHV-1 targets endothelial cells (cells lining blood vessels) and parenchymal cells (working cells of organs)
• The virus causes necrosis (cell death) and hemorrhage in every organ it reaches:
  • Lungs → focal necrosis and hemorrhage → respiratory failure
  • Kidneys (cortex) → necrosis and petechiae
  • Adrenal glands → necrosis
  • Liver → multifocal hepatic necrosis
  • GI tract → hemorrhagic enteritis
  • Lymph nodes → enlargement and necrosis
  • Spleen → splenomegaly and necrosis
  • Brain → meningoencephalitis, cerebellar hypoplasia, necrosis
  • Eyes → retinal necrosis, blindness

• Death usually occurs 24–36 hours after onset of clinical signs
• The incubation period (exposure to first signs) is 4–6 days
• Entire litters can be wiped out within 24 hours

Why Is There No Fever? — CRITICAL EXAM POINT

• There is NO fever (or it is very low-grade)
• Because the puppy's body temperature is already low (35–36°C) — the virus keeps temperature suppressed
• A sick neonatal puppy WITHOUT fever should always raise suspicion for CHV-1
• This is how CHV-1 differs from most other infections

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In Pregnant Bitches (Acute Primary Infection)

• If a bitch has never been exposed to CHV-1 before and gets infected during the last 3 weeks of pregnancy, the virus can:
  • Cross the placenta (transplacental infection)
  • Cause fetal death, mummification, resorption
  • Lead to abortion (spontaneous termination of pregnancy)
  • Cause premature delivery of stillborn or weak, infected puppies
• The bitch herself usually shows no or only mild symptoms (nasal discharge, vaginal discharge)
• If a bitch was previously exposed and has antibodies, she may still reactivate and shed virus during whelping, but her antibodies provide some protection via colostrum to her puppies

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In Adult Dogs (Chronic/Latent Infection)

• After primary infection, CHV-1 retreats to the trigeminal ganglion and becomes latent (dormant)
• The dog's immune system CANNOT eliminate the virus from the ganglion
• Periodically, with stress or immunosuppression → reactivation → virus travels back down the nerve → shedding in oral, nasal, or genital secretions
• This cycle continues for the dog's entire life

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In the Nervous System (Surviving Puppies)

• Puppies aged 3–5 weeks that survive neonatal CHV-1 may develop permanent neurological damage because:
  • The virus damages the developing cerebellum (balance center) → permanent ataxia
  • Damages the optic nerve and retina → permanent blindness
  • Destroys the vestibular apparatus → persistent head tilt, balance problems
  • Causes cerebellar hypoplasia (underdevelopment of the cerebellum)

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PART 5 — CLINICAL SIGNS

A. Neonatal Puppies (< 3 weeks old)

• Persistent, constant crying / vocalization (the puppy cries incessantly — pain from abdominal lesions)
• Anorexia — stops nursing, refuses milk, cannot suckle
• Weakness, depression, lethargy — the puppy becomes limp, soft
• Hypothermia (low body temperature) — cold to touch
• Abdominal pain — abdomen looks distended and painful on palpation
• Nasal discharge — serous to mucopurulent
• Dyspnea / tachypnea — breathing difficulty (lung involvement)
• Soft/yellow-green diarrhea
• Petechiae (pinpoint red hemorrhages) on:
  • Gums (oral mucous membranes)
  • Inner ear flap
  • Conjunctiva (whites of the eyes)
  • Abdomen and skin
• Loss of righting reflex — puppy cannot turn itself over
• No fever (this is pathognomonic — absence of fever in a severely ill neonate)

• Day 0: Exposure (birth or first days of life)
• Day 4–6: First signs appear (crying, not nursing)
• Day 5–7: Rapid deterioration
• Death within 24–36 hours of first visible signs

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B. Puppies 3–5 Weeks Old

• Generally less severe because they can somewhat regulate body temperature
• More likely to survive but with long-term consequences
• Clinical signs:
  • Mild to moderate lethargy, poor growth
  • Mild respiratory signs
  • Some will develop neurological signs as they grow:
    • Ataxia (wobbling, difficulty walking, falling)
    • Blindness (partial or complete)
    • Head tilt (vestibular damage)
    • Deafness (inner ear damage)
    • Cerebellar hypoplasia — puppies that seem "clumsy" even after full recovery

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C. Pregnant Bitches

• Often asymptomatic (no visible illness)
• May show:
  • Mild vaginal discharge (serous or mucopurulent)
  • Mild nasal discharge
  • Lethargy
• Reproductive consequences:
  • Abortion in mid-to-late pregnancy
  • Stillborn puppies
  • Resorption of fetuses (early pregnancy loss)
  • Premature delivery of weak, dying puppies
  • Infertility — repeated pregnancy losses with no other explanation
  • Producing live puppies that rapidly die (fading puppy syndrome)

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D. Adult Dogs (Non-Pregnant)

• Mild upper respiratory infection
• Serous nasal discharge
• Sneezing
• Cough (may be part of "Kennel Cough" / infectious tracheobronchitis complex)
• Tonsillitis
• Usually self-limiting — resolves without treatment

• Females: Vesicular vaginitis — small fluid-filled blisters/vesicles on the vaginal mucosa; reddened, inflamed vaginal lining; mucopurulent vaginal discharge
• Males: Balanoposthitis (posthitis) — vesicles and inflammation of the prepuce and glans penis; discharge from prepuce; dog may lick the area excessively
• Both forms are usually mild and self-limiting

• Conjunctivitis — redness, discharge
• Blepharitis — eyelid inflammation
• Ulcerative keratitis — painful corneal ulcers, often dendritic (branching) pattern — classic herpesvirus corneal ulcer shape
• Non-ulcerative keratitis — corneal cloudiness without open ulcer
• Occurs during primary infection or reactivation
• Particularly important in dogs receiving immunosuppressive drugs (steroids, cyclosporine) — reactivation can cause serious eye disease (Ledbetter, NZ Vet J 2013 [PMID: 23438442]; Soleimani et al. 2025 [PMID: 41259018])

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PART 6 — GROSS PATHOLOGY & HISTOPATHOLOGY

Gross (Macroscopic) Lesions at Necropsy — CLASSIC PICTURE

Disseminated focal necrosis AND hemorrhages throughout multiple organs

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Histopathology (Microscopic Lesions)

• Necrosis in parenchymal cells of affected organs
• Hemorrhage into the adjacent tissue
• Minimal inflammatory reaction — because the immune system is immature and overwhelmed
• Intranuclear inclusion bodies — eosinophilic (pink-staining) inclusions within nuclei of infected cells
  • Cowdry Type A inclusions are typical of herpesviruses
  • Found in epithelial cells of kidneys, liver, lungs, adrenals
• In the brain: meningitis, perivascular cuffing, glial nodules, and neuronal necrosis
• In the eye: retinal necrosis and optic neuritis

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PART 7 — DIAGNOSIS

Step 1 — Clinical Suspicion

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Step 2 — Diagnostic Tests

Post-Mortem (Necropsy) Diagnosis — Most Reliable for Neonates

Ante-Mortem (Live Dog) Diagnosis

• CHV-1 antibody titers drop very quickly — within 1–2 months of infection
• A dog can be actively infected but seronegative (negative antibody test)
• A negative serology does NOT mean a dog is free of CHV-1
• PCR is the preferred diagnostic method for active infection

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Differential Diagnosis — What Else Causes Similar Signs?

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PART 8 — TREATMENT

Critical Reality Check First:

There is no specific licensed antiviral drug approved for CHV-1 treatment in dogs. Treatment is primarily supportive. In neonates, treatment is often unrewarding because the disease progresses within hours.

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Treatment of Neonatal Puppies

1. Warming Therapy — MOST IMPORTANT FIRST STEP

• Raise the puppy's body temperature to 37–38.5°C (98.6–101°F)
• Use:
  • Incubator set to 35°C (95°F) ambient temperature at 50% relative humidity
  • Warming box with a heat lamp
  • Heating pad (be careful — do not burn the puppy; use a towel as a buffer)
• Why it works: CHV-1 cannot replicate efficiently above 37°C. Raising body temperature directly suppresses viral replication.
• This is the single most important intervention in neonatal CHV-1
• Note: Recent evidence suggests warming alone may not fully stop disease progression once signs appear, but it significantly reduces losses in exposed but not-yet-symptomatic littermates

2. Passive Immunization (Hyperimmune Serum)

• Collect serum from a seropositive adult female dog (previously exposed, has antibodies)
• Inject intraperitoneally (IP) into exposed puppies before signs appear
• The maternal antibodies provide passive immunity to neutralize the virus
• This is most effective as prophylaxis (prevention before signs) rather than treatment
• Can also transfer the litter to a seropositive nursing female — her colostrum provides protective antibodies

3. IV/Oral Fluid Therapy

• Dehydration develops rapidly
• Administer warmed fluids:
  • Subcutaneous or intraperitoneal routes in neonates (veins too small for IV in very young pups)
  • Balanced electrolyte solution (Normal Saline or Lactated Ringer's)
  • Add dextrose (glucose) to prevent hypoglycemia
• Rate: Based on hydration status and puppy weight

4. Nutritional Support

• If puppy cannot nurse: tube feeding with puppy milk replacer
• Small, frequent feeds (every 2 hours in neonates)
• Keep warm before and during feeding

5. Antiviral Drugs (Limited Evidence)

• Acyclovir (Zovirax):
  • A nucleoside analogue that inhibits viral DNA polymerase
  • Works well against human herpesviruses
  • In vitro activity against CHV-1 demonstrated
  • Clinical effectiveness in dogs is uncertain — limited studies
  • Can be used as part of treatment but should not be relied upon as the primary intervention
  • Dose: varies; consult a veterinary pharmacologist
  • May be toxic at high doses
• Cidofovir and Ganciclovir — investigated in research settings; not routine clinical use

6. Antibiotics

• CHV-1 is a virus — antibiotics do NOT kill it
• BUT: Use antibiotics to prevent or treat secondary bacterial infections (pneumonia, septicemia) in weakened puppies
• Common choices: Amoxicillin, Ampicillin (IV in neonates)

7. Oxygen Therapy

• For puppies with respiratory distress (lung involvement)
• Use an oxygen cage or flow-by oxygen

8. Supportive Nursing

• Keep puppies clean and dry
• Ensure they are feeding
• Isolate affected puppies from others in the kennel

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Treatment of Adult Dogs

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Prognosis Summary

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PART 9 — PREVENTION & CONTROL

1. Vaccination

• A commercial vaccine exists: Eurican Herpes 205 (Merial/Boehringer Ingelheim)
• Inactivated (killed) CHV-1 vaccine
• Indicated for use in breeding bitches to protect future litters
• Vaccination schedule:
  • First dose: during proestrus/estrus (when the bitch comes into heat)
  • Second dose: 1–2 weeks before expected whelping
  • Revaccinate with every pregnancy
• The vaccine does NOT prevent infection but stimulates high antibody levels in the dam → antibodies passed to puppies in colostrum → passive protection for the litter
• NOT a lifelong vaccine — immunity from CHV-1 antibodies is short-lived (weeks to months), so revaccination with every breeding is necessary

• As of the time of this writing, no licensed CHV-1 vaccine is available in the USA
• Prevention relies on management practices

2. Management Practices (Most Important in Non-Vaccinated Countries)

• Isolate the pregnant bitch for the last 3 weeks of gestation — away from all other dogs
• Keep the dam and puppies isolated for 3 weeks after birth
• This prevents exposure to shedding carrier dogs during the most vulnerable period
• The litter's "safe window" is: from 3 weeks before birth to 3 weeks after birth

• Keep the whelping environment at 29–32°C (84–90°F) ambient temperature for the first 2 weeks
• Puppies should not drop below 35.5°C (96°F) body temperature
• Use a thermometer to check puppy body temperatures regularly
• Incubator, heat lamp, or under-blanket heating mat are acceptable

• Ensure every puppy nurses within the first 12–24 hours of life to receive maternal antibodies via colostrum
• If dam is known seronegative (no antibodies), consider sourcing colostrum from a seropositive female

• Disinfect whelping box and equipment with bleach (1:30 dilution) or Virkon
• Wash hands thoroughly between handling litters
• Do not share equipment between litters

• Test breeding dogs for CHV-1 via PCR (swabs) or serology before breeding
• Paired serology (2 samples 2–3 weeks apart) showing seroconversion confirms recent active infection

• Minimize stress for breeding dogs — stress is the main trigger for viral reactivation
• Avoid transporting pregnant bitches to new environments
• Provide stable, calm whelping environments

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PART 10 — LATENCY AND REACTIVATION (Advanced Concept)

Where Does the Virus Hide?

What Triggers Reactivation?

What Happens During Reactivation?

• Virus travels back down the nerve to the mucosal surface
• Dog begins shedding virus in oral, nasal, or genital secretions
• Often completely asymptomatic — the dog looks healthy but is spreading virus
• This is why CHV-1 persists in dog populations despite vaccination efforts — seroprevalence approaches 80% in kennels because most infected adult carriers shed periodically without owners knowing
• It is biologically impossible to eradicate CHV-1 from a kennel once it is present

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PART 11 — QUICK REFERENCE SUMMARY TABLE

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PART 12 — FREQUENTLY ASKED QUESTIONS (FAQ)

Questions from Pet Owners:

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1. Isolation — keep the pregnant bitch away from all other dogs for the last 3 weeks before whelping
2. Vaccinate (if you are in Europe — Eurican Herpes vaccine with each pregnancy)
3. Whelping box temperature — keep it warm (29–32°C ambient) so puppies maintain a body temperature > 37°C
4. Ensure puppies nurse within 12 hours of birth for colostrum protection

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• Start warming therapy immediately
• Administer hyperimmune serum if available
• Provide fluid and glucose support
• Run PCR testing for confirmation

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• Perform PCR of nasal, oral, and vaginal swabs to check for active shedding
• Run serology (ELISA) to check antibody status
• If seronegative: protect the bitch carefully during breeding and pregnancy from exposure
• If seropositive: she carries the virus; vaccination (where available) before each pregnancy is recommended

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• Merck Veterinary Manual — Canine Herpesvirus Infection
• Decaro N, Martella V, Buonavoglia C — Canine adenoviruses and herpesvirus. Vet Clin North Am Small Anim Pract 2008 [PMID: 18501279]
• Ledbetter EC — Canine herpesvirus-1 ocular diseases of mature dogs. NZ Vet J 2013 [PMID: 23438442]
• Soleimani S et al. — Prevalence and Clinical Impacts of CHV-1 in Dogs: A Review. Vet Med Sci 2025 [PMID: 41259018]
• Dr. Emmanuel Fontaine — Why Is Canine Herpes So Hard to Eliminate? (2026)
• AKC — Canine Herpes Virus: What Breeders Should Know
• Texas A&M Veterinary Medical Diagnostic Laboratory — CHV Case Studies (2024)
• Jawetz, Melnick & Adelberg's Medical Microbiology 28e (Herpesviridae classification)

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