Acepromazine
Acne
Acral Lick Granulomas
Addison's disease
Adenovirus Type 2
Aggression - intercat
Agression
Allergies & Hay Fever
Anal Sac Problems
Anemia
Arthritis
Asthma
Attacks (Ankle Biting)
Back & Disk Problems
Bad Breath
Barking
Begging
Behavior - Destructive Scratching
Birthing
Bites
Bladder
Bleeding
Bordetella
Boredom
Brucellosis
Burrs
Canine Distemper Virus
Car Chasing
Car sickness
Cardiologist
Cardiomyopathy
Cat Blood Types
Cat Flu
Cataract Surgery
Cataracts
Cerebellar Hypoplasia
Chewing
Chlamydiosis
Chocolate toxicity
Claw Problems
Cold Weather
Congenital Heart Disease
Constipation
Coomb's test
Coprophagia
Coronavirus Vaccination
Coughing
Craniomandibular Osteopathy
Cushing's Disease
D-ACVR
Dandruff
Deafness
Declawing
Degree of Luxation
Dehydration
Dental Problems
Depression
Destructive Behavior
Diabetes
Diabetes - sudden onset or ketoacidotic diabetes
Diabetes Control
Diabetes Insipidus
Diabetes mellitus
Diabetes Mellitus or Type 1 Diabetes
Diarrhea
Diarrhea - Chronic
Digging
Distemper Vaccination
Distichiasis
Dizziness
DNA (deoxyribonucleic acid)
DNA General Information
DNA Profile
Dominant
Drooling
Dung Eating
DVM
Ear Mites
Ehrlichiosis
Elbow Dysplasia
Epilepsy and Seizure.
Estrus or Heat cycle
Eye Irritation
Fears
Feeding your pet
Feline Infectious Peritonitis (FIP)
Feline Leukemia
Feline Leukemia Treatment
Femoral Head Ostectomy
Fever
Fibrosarcoma
Fibrosarcoma - Vaccine Related
Fighting
Flatulence
Flea Control
Flea Life Cycle
Fleas
Food Allergy & Sensitivity
Fussy Eating
General Legg-Calve-Perthes Information
General Thyroid Information
Genes
Genetics of Deafness in Dogs
Genotype
Giardia
Hair Balls
Heart murmur
Heart Problems
Heartworm Disease
Heartworm Disease Testing
Heartworm Treatment
Heartworms
Heat cycle
Hemangiosarcoma
Hemolytic Anemia
Hemorrhagic Gastroenteritis (HGE)
Hepatic Lipidosis
Heterozygous
Hip Dysplasia
Hives
Homozygous
Hot Spots
Hot Spots or Acute Moist Pyoderma
Hot Weather Concerns
House Training
Hygroma
Hyperadrenocorticism
Hyperthyroidism
Hypertrophic Osteodystrophy (HOD)
Hypoadrenocorticism
Hyposomatotrophism
Illness - Caring for your pet
Immune Mediated Hemolytic Anemia
In Heat
Insect Bites & Stings
Insulin Regulation
Intussusception
Itch Control
Itching
Jealousy
Jumping Up
Kennel cough
Keratoconjunctivitis (CIKS)
Lameness
Legg-Calve-Perthes Disease (aseptic or avascular necrosis of the femoral head)
Leishmaniasis
Leptospirosis Vaccination
Lice
Licking
Lipoma
Litterpan Behavior Problems
Liver shunt
Lumps & Bumps
Lupus Erythematosus
Lupus, Discoid
Lyme Disease (Borrelia) Bacterin
Malassezia ear infection
Mange
Mating Problems
Matted Coat
Megacolon
Megaesophagus
Mendelian Inheritance
Meowing
Moist Pyoderma
Monogenic
Moving Anxiety
MS
Myasthenia Gravis
Nausea
Nipping & Biting
Noise Anxiety
Nosebleeds
Odor
Overwieght
Palpation
Pancreatitis
Panosteitis
Parainfluenza Vaccination
Paroxysmal Respiration
Parvovirus
Parvovirus - Transmission
Parvovirus Vaccination
Paw
Pemphigus
Perianal Adenoma
Phenotype
Pilling a cat
Pituitary Dwarfism or Hyposomatotrophism
Pityrosporum
Pneumothorax
Poisoning
Polygenic
Porcupine Quills
Pregnancy
Pregnancy - False
Prolapse
Prostate Problems
Pruritis
Rabies Vaccination
Radial Nerve Paralysis
Recessive
Reproduction - When to Breed
Reproduction - When to Neuter
Reproduction - When to Spay
Rhinotracheitis
Ringworm
Salivation
Schnauzer Comedone Syndrome
Sebaceous Adenitis Information
Seizure Activity
Seizure Control
Separation Anxiety
Shedding
Sinus Problems
Skunk Spray
Sleeping Problems
Spay/Neuter - Early
Specialist
Spine
Spondylosis
Spontaneous Iris Melanosis
Spraying
Squamous Cell Carcinoma
Sublaxation, Hip
Sunburn
Tail Problems
Teething
The Dysplastic Joint
The Three Faces of Elbow Dysplasia
Ticks
Tracheobronchitis
Transitional Vertebrae
Tree Cats
Triple Pelvic Osteotomy (TPO)
Ulcers
Unilateral dysplasia
Urinary Tract Infections
Urination, submissive and excitement
Vaginal prolapse
Vascular Ring Anomaly
Vena Caval Syndrome
Vestibular Syndrome
Vision - How dogs see
Vision Problems
Vomiting
What is Patellar Luxation?
Whisker Problems
White Dog Shaker Syndrome
Wool Sucking
Worms
Wounds
Saturday Dec 8, 2007 11:02 AM EST
Acne
Acral Lick Granulomas
Addison's disease
Adenovirus Type 2
Aggression - intercat
Agression
Allergies & Hay Fever
Anal Sac Problems
Anemia
Arthritis
Asthma
Attacks (Ankle Biting)
Back & Disk Problems
Bad Breath
Barking
Begging
Behavior - Destructive Scratching
Birthing
Bites
Bladder
Bleeding
Bordetella
Boredom
Brucellosis
Burrs
Canine Distemper Virus
Car Chasing
Car sickness
Cardiologist
Cardiomyopathy
Cat Blood Types
Cat Flu
Cataract Surgery
Cataracts
Cerebellar Hypoplasia
Chewing
Chlamydiosis
Chocolate toxicity
Claw Problems
Cold Weather
Congenital Heart Disease
Constipation
Coomb's test
Coprophagia
Coronavirus Vaccination
Coughing
Craniomandibular Osteopathy
Cushing's Disease
D-ACVR
Dandruff
Deafness
Declawing
Degree of Luxation
Dehydration
Dental Problems
Depression
Destructive Behavior
Diabetes
Diabetes - sudden onset or ketoacidotic diabetes
Diabetes Control
Diabetes Insipidus
Diabetes mellitus
Diabetes Mellitus or Type 1 Diabetes
Diarrhea
Diarrhea - Chronic
Digging
Distemper Vaccination
Distichiasis
Dizziness
DNA (deoxyribonucleic acid)
DNA General Information
DNA Profile
Dominant
Drooling
Dung Eating
DVM
Ear Mites
Ehrlichiosis
Elbow Dysplasia
Epilepsy and Seizure.
Estrus or Heat cycle
Eye Irritation
Fears
Feeding your pet
Feline Infectious Peritonitis (FIP)
Feline Leukemia
Feline Leukemia Treatment
Femoral Head Ostectomy
Fever
Fibrosarcoma
Fibrosarcoma - Vaccine Related
Fighting
Flatulence
Flea Control
Flea Life Cycle
Fleas
Food Allergy & Sensitivity
Fussy Eating
General Legg-Calve-Perthes Information
General Thyroid Information
Genes
Genetics of Deafness in Dogs
Genotype
Giardia
Hair Balls
Heart murmur
Heart Problems
Heartworm Disease
Heartworm Disease Testing
Heartworm Treatment
Heartworms
Heat cycle
Hemangiosarcoma
Hemolytic Anemia
Hemorrhagic Gastroenteritis (HGE)
Hepatic Lipidosis
Heterozygous
Hip Dysplasia
Hives
Homozygous
Hot Spots
Hot Spots or Acute Moist Pyoderma
Hot Weather Concerns
House Training
Hygroma
Hyperadrenocorticism
Hyperthyroidism
Hypertrophic Osteodystrophy (HOD)
Hypoadrenocorticism
Hyposomatotrophism
Illness - Caring for your pet
Immune Mediated Hemolytic Anemia
In Heat
Insect Bites & Stings
Insulin Regulation
Intussusception
Itch Control
Itching
Jealousy
Jumping Up
Kennel cough
Keratoconjunctivitis (CIKS)
Lameness
Legg-Calve-Perthes Disease (aseptic or avascular necrosis of the femoral head)
Leishmaniasis
Leptospirosis Vaccination
Lice
Licking
Lipoma
Litterpan Behavior Problems
Liver shunt
Lumps & Bumps
Lupus Erythematosus
Lupus, Discoid
Lyme Disease (Borrelia) Bacterin
Malassezia ear infection
Mange
Mating Problems
Matted Coat
Megacolon
Megaesophagus
Mendelian Inheritance
Meowing
Moist Pyoderma
Monogenic
Moving Anxiety
MS
Myasthenia Gravis
Nausea
Nipping & Biting
Noise Anxiety
Nosebleeds
Odor
Overwieght
Palpation
Pancreatitis
Panosteitis
Parainfluenza Vaccination
Paroxysmal Respiration
Parvovirus
Parvovirus - Transmission
Parvovirus Vaccination
Paw
Pemphigus
Perianal Adenoma
Phenotype
Pilling a cat
Pituitary Dwarfism or Hyposomatotrophism
Pityrosporum
Pneumothorax
Poisoning
Polygenic
Porcupine Quills
Pregnancy
Pregnancy - False
Prolapse
Prostate Problems
Pruritis
Rabies Vaccination
Radial Nerve Paralysis
Recessive
Reproduction - When to Breed
Reproduction - When to Neuter
Reproduction - When to Spay
Rhinotracheitis
Ringworm
Salivation
Schnauzer Comedone Syndrome
Sebaceous Adenitis Information
Seizure Activity
Seizure Control
Separation Anxiety
Shedding
Sinus Problems
Skunk Spray
Sleeping Problems
Spay/Neuter - Early
Specialist
Spine
Spondylosis
Spontaneous Iris Melanosis
Spraying
Squamous Cell Carcinoma
Sublaxation, Hip
Sunburn
Tail Problems
Teething
The Dysplastic Joint
The Three Faces of Elbow Dysplasia
Ticks
Tracheobronchitis
Transitional Vertebrae
Tree Cats
Triple Pelvic Osteotomy (TPO)
Ulcers
Unilateral dysplasia
Urinary Tract Infections
Urination, submissive and excitement
Vaginal prolapse
Vascular Ring Anomaly
Vena Caval Syndrome
Vestibular Syndrome
Vision - How dogs see
Vision Problems
Vomiting
What is Patellar Luxation?
Whisker Problems
White Dog Shaker Syndrome
Wool Sucking
Worms
Wounds
Heartworm Disease Testing
There are several ways to test for heartworms. The first method developed was to put a drop of blood on a microscope slide and look for baby heartworms, which are microscopic and are known as microfilaria. This works if there are adult heartworms producing babies and if the dog's immune system is not killing the babies. It is probably an accurate test for adult heartworms in about 50 to 60% of infected dogs (just an educated guess on the percentages). The accuracy of this type of testing was improved by using "concentration" techniques --- methods of increasing the likelihood of finding microfilaria if only a few were present. Originally this involved centrifuging blood but later special microfilters were developed to allow filtering of baby heartworms out of a bigger blood sample. This was a better test but still was inaccurate if the heartworms weren't producing babies or if the dog's immune system was killing them. Estimates of the inaccuracy of this testing varied widely but the general consensus was that it missed between 20 and 30% of heartworm cases and I personally think it was probably higher than that. Testing for microfilaria was critically important when daily heartworm medications were in use. Ironically, the presence of microfilaria was actually more important than the presence of the adult heartworms when using these preventatives because reactions could occur that could cause death when daily preventatives were given to dogs with microfilaria in their circulation. There was not much incentive to get more accurate in testing for heartworms in order to use preventative but a number of dogs still had clinical signs of heartworm disease and yet tested negative on available blood tests. Tests for antibodies to heartworms were developed. These were problematic because they indicated exposure to the heartworms, so dogs remained positive on these tests even if heartworms had died naturally or after successful treatment. Finally, tests were developed that test directly for adult heartworm antigen -- but only from adult, sexually mature female heartworms. So now there are two situations in which the testing remains inaccurate -- all male heartworm infections and heartworm infections in which there are female heartworms present that are less than 6 or 7 months of age. There is also a small possibility of a false positive test with the antigen test kits -- estimates are that it is about 1 in 1000.
So how does this apply to your dog? The first test could be accurate and the second test a false positive. The odds of this are low but it is possible. The presence of clinical signs makes the odds very very low, in fact. The test may have been a filtration or concentration test for microfilaria and your dog may not have microfilaria despite having adult heartworms. The test may have been an antigen test and your dog may have been infected at the time of the first test but for less than 6 months -- so there were no adult females to make the test positive. Now, months later, the females have grown up and are causing problems. In any case, treatment is now indicated.
