Understanding MCADD in Canines
Medium Chain Acyl-CoA Dehydrogenase Deficiency (MCADD) is a metabolic disorder that poses a significant health risk for certain breeds like Cavalier King Charles Spaniels (CKCS). This genetic condition impairs the dog's ability to metabolize medium-chain fatty acids found in oils such as coconut, palm, and kernel oils, preventing their use as an alternative energy source when glucose is unavailable. In severe cases, it can lead to coma or sudden death, particularly during fasting or periods of illness.
Affected dogs will exhibit symptoms during times of increased metabolic demand when their bodies cannot use these fats for energy. However, the condition can be effectively managed through a low-fat diet, which mitigates the inability to metabolize these specific fats and helps maintain stable glucose levels.
What is MCADD?
MCADD is caused by a mutation in the ACADM gene, which is responsible for producing the enzyme medium-chain acyl-CoA dehydrogenase. This enzyme is crucial for the breakdown of medium-chain fatty acids into energy. Without it, affected dogs cannot efficiently convert these fats into energy, leading to a buildup of unmetabolized fatty acids and a shortage of usable energy during times of metabolic stress.
Symptoms of MCADD
Dogs with MCADD may remain asymptomatic until they undergo metabolic stress, such as fasting, illness, or intense physical activity. Common symptoms include:
Lethargy: A lack of energy and prolonged periods of inactivity.
Vomiting: Often associated with low blood sugar levels.
Hypoglycaemia: Critically low blood sugar levels leading to weakness and confusion.
Muscle Weakness: Generalised weakness and inability to engage in normal activities.
Seizures: Recurrent and cluster seizures, sometimes lasting up to 24 hours.
Central Nervous System Dysfunction: Manifesting as disorientation, uncoordinated movements, or even coma.
Sudden Death: In severe cases, especially if untreated during a hypoglycaemic episode.
Diagnosis
Diagnosis of MCADD involves several steps:
1. Genetic Testing: DNA testing is the gold standard for diagnosing MCADD. Genetic testing laboratories can identify the ACADM gene mutation from a saliva sample. Laboratories like Laboklin, Canine Genetic Testing, and GenSol Animal Diagnostics offer such tests for under £60.
2. Blood and Urine Tests: These tests can detect organic aciduria with excessive excretion of hexanoylglycine and elevated medium-chain fatty acids, which are indicative of MCADD.
Determining DNA results
Understanding Your Genetic Test Results for Medium Chain Acyl-CoA Dehydrogenase Deficiency is relatively simple.
A. Clear/Normal:
Dogs with two copies of the normal gene will neither develop Medium Chain Acyl-CoA Dehydrogenase Deficiency (MCADD) nor transmit this genetic mutation to their offspring.
B. Carrier/Not Affected:
Dogs possessing one normal gene and one mutated gene are carriers. While they will not exhibit symptoms of MCADD, they have a 50% chance of passing the mutation to their puppies.
C. At Risk/Affected:
Dogs with two copies of the mutated gene are at a high risk of developing MCADD and are likely to manifest symptoms associated with this condition.
Research and Prevalence
Studies have shown that MCADD is relatively common among CKCS:
A 2022 study examined 162 Cavaliers and found that 52 were carriers of the ACADM mutation, and 12 were homozygous mutants (affected) .
Approximately 10% of all Cavaliers may be affected by MCADD, and over half of the breed may carry the mutation .
Management and Treatment
Effective management of MCADD focuses on diet and avoiding fasting.
Diet: Affected dogs should be fed a, low-fat diet with carbohydrates. Avoiding foods containing medium-chain triglycerides (MCTs) such as coconut oil and palm kernel oil, as these cannot be metabolised properly by MCADD-affected dogs. We recommend thoroughly checking the labels of all food treats and bowl add ons given as even more species appropriate fresh foods such as British brand, Luna & Me contains coconut oil, as do many dog treats contain vegetable glycerin etc.
Complex carbohydrates; studies of MCADD in humans shows the addition of complex carbohydrates helped to prevent hypoglycaemia.
Some carbs that are healthy for dogs and can be added to their diet are; oats (in moderation), quinoa, sweet potato, sweet potato, pumpkin, butternut squash, blueberries, bananas, peaches, mangoes and strawberries. It is recommended to increase calories with extra complex carbohydrates during illness or stress.
Frequent Meals: Providing frequent meals and snacks, especially before bedtime, helps maintain stable blood sugar levels and prevent hypoglycaemic episodes.
Emergency Protocols: In case of illness or increased metabolic stress, glucose supplements or a simple carbohydrate treat may be necessary to prevent hypoglycaemia.
Foods to Avoid
Owners should be vigilant about the ingredients in their dog's diet. Foods containing MCTs that should be avoided include:
Coconut Products: Coconut oil, coconut milk, coconut cream, coconut meat, coconut meal, and coconut flour.
Palm Kernel Oil: Commonly found in processed pet foods.
Dairy Products: cows milk, goats milk, sheep’s milk, butter, hard cheeses (e.g., cheddar, parmesan), feta cheese and Greek yogurt.
Goat's Milk: Particularly whole goat's milk fat.
Vegetable Glycerin: Often used as a sweetener in pet treats.
Practical Tips for Owners and Breeders
Regular Vet Visits: Regular veterinary check-ups are essential for monitoring the health of dogs with MCADD.
Genetic Testing: Breeders should test their breeding stock for the ACADM mutation to prevent producing affected puppies. Pet owners should also test their dogs before introducing any MCT-containing foods.
Emergency Preparedness: Owners should have an emergency plan, including glucose supplements and a clear understanding of the signs of hypoglycaemia.
Conclusion
MCADD is a serious but manageable condition with proper care and dietary management. Genetic testing and informed breeding practices can help reduce the prevalence of MCADD in Cavalier King Charles Spaniels. By adhering to dietary guidelines and monitoring their health closely, owners can ensure that their dogs lead healthy, happy lives.
References
1. "MCADD in the Cavalier King Charles Spaniel," CavalierHealth.org.
2. "Genetic Studies and Case Reports on MCADD in CKCS," CavalierHealth.org.
https://www.mayoclinic.org/diseases-conditions/mcad-deficiency/diagnosis-treatment/drc-20353747
