Genetic Testing Test #1 - MDR1 A mutation in the canine MDR1 gene (multidrug resistance gene) leads to a hypersensitivity to multiple drugs including Ivermectin (antiparasitic drug). Ivermectin hypersensitivity based on MDR1 gene mutation was proved in several breeds including the Australian Shepherd. The introduction of antiparasitic drug Ivermectin in 1980 revealed new inherited disease in several dog breeds. Ivermectin potentiates chloride ion channels in the peripheral nervous system, causing lethal paralysis of some invertebrates parasites. If administered to defective animals, administering of ivermectin or a similar drug can lead to elevated levels of a drug in the CNS, resulting in a potentially lethal neurotoxic reaction. These drugs include but are not limited to Acepromazine, Butorphanol, Doramectin, Doxorubicin, Ivermectin, Loperamide, Milbemycin, Moxidectin, Selamectin, Vinblastine, Vincristine. MDR1 related drug hypersensitivity is inherited as an autosomal recessive trait. That means the disease affects dogs with P/P genotype only. The dogs with P/N genotype are considered carriers of the disease (heterozygotes). In offspring of two heterozygous animals following genotype distribution can be expected: 25% N/N (healthy noncarriers), 25% P/P (affected), and 50% N/P (healthy carriers). Because of the high risk of producing affected offspring, the mating of two N/P animals (carriers) can not be recommended. Test #2 - PRCD/PRA PRA -PRCD disease information: a Late form of Progressive Retinal Atrophy, called PRA-prcd (progressive rod-code degeneration), is just one of all retinal defects. Rods degenerate at first. Affected dogs become night-blind. This is very often the first symptom that dog owners recognize. Dogs usually have a poor sense of directions and they crash into things. A pupil is widely open even when a direct ray of light hits the eye (dogs have shining eyes in pictures). Later, cones start degenerating. Final disease symptoms are cataracts and total blindness. PRA-prcd is a hereditary disease. Causal mutation G1298A in a ninth canine chromosome (CFA9) PRA-prcd was recognized. This mutation is inherited as an autosomal recessive trait. That means that disease affects dogs with P/P genotype only. The dogs with P/N genotype are considered carriers of the disease (heterozygotes). In offspring of two heterozygous animals following genotype distribution can be expected: 25% N/N (healthy non-carriers), 25% P/P (affected), and 50% N/P (healthy carriers). Because of the high risk of producing affected offspring, a mating of two N/P animals (carriers) can not be recommended. Test #3 - HC Hereditary cataract (HC) Cataract is an eye disorder affecting the lens transparency. Cataracts are very often inherited and occur in more than 70 dog breeds. In connection with the hereditary forms of cataracts in dogs, there have been described several modes of inheritance, the majority being autosomal recessive. There are also autosomal dominant or polygenic modes of inheritance. Cataracts are the leading cause of blindness in dogs. The hereditary cataracts are often called primary cataracts. Secondary cataracts are forms of a cataract that accompany other eye disorders, for example, progressive retinal atrophy, glaucoma, retinal dysplasia, metabolic diseases and other disorders. Cataracts may develop after an eye injury (traumatic cataracts) or are related to aging (senile cataracts). The cataracts are very specific in individual breeds with regard to the affected parts of the lens, an age of disease onset, progression rate and the rate of bilateral development of the cataract. The presence of deletion is significantly associated with the development of binocular cataracts at various ages. The HC disorder in Australian Shepherds has an autosomal dominant mode of inheritance, however with incomplete penetrance. It means that the disease may not develop in every carrier of this deletion and effects of other genetic factors or environmental factors are not excluded. The probability that the binocular HC develops in individuals with one copy of deletion (carriers) is approximately 17 times higher than in dogs clear of the deletion mutation. The carriers of the mutation pass it on to their offspring and therefore, it is necessary to avoid mating two heterozygous dogs as 25% of puppies born will be homozygous.