Small-size dogs, or Toy dogs, suffer breed specific problems, and the Chihuahua is not an exception. There are several congenital diseases that might present serious health risk in this breed, such as patellar luxation, heart diseases and eye abnormalities. If the timely and correct preventive care is provided and if the breeding stock is free from genetic defects, then you have a healthy Chihuahua.
Patellar luxation, a common congenital or acquired orthopedic abnormality. The patella or kneecap is a small bone buried in the tendon of the extensor muscles (the quadriceps muscles) of the thigh. The tendon is a band of tough, inelastic tissue that connects a muscle with its bony attachment. With this condition, the kneecap may slip out of the tendon and then slip back. Patellar Luxation is graded 1 to 4 based on the severity of the defect, 1 being occasional mild lameness.
Progressive retinal atrophy (PRA) is a collective term comprising a group of hereditary degenerative lesions of the retina. Generalized PRA is characterized by night blindness with both eyes affected and dogs eventually become totally blind. Central PRA (also called RPE dystrophy) is marked by accumulations of pigment in the layer of pigmented lining of the retina, which results in day blindness and eventually terminates in total blindness.
Transient juvenile hypoglycemia, which is brought on by fasting, is common in Toy dog breeds, such as Yorkshire Terrier, Toy Poodle, Pomeranian and other Toy dog breeds, and usually seen in puppies 5 to 16 weeks of age.
Cryptorchidism, a developmental defect of the testes. The testes (testicles) develop in the abdomen and gradually descend into the scrotum. They should be present there at birth, or shortly after. If they have not descended by the time the dog is adult, he can be described as either a unilateral cryptorchid (when one testis is still retained in the abdomen), or bilateral cryptorchid (when both have not descended). The testis that remains in the abdomen does not function and has a high risk of being injured or twisted. The undescended testis is affected by cancer more often then the normal descended testis. Sometimes, the hidden testes may descend when a puppy is 6 months of age. It is advised to check with your veterinarian at the time of vaccination.
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Hydrocephalus is the malfunction of drainage system of the brain responsible for evacuating the cerebrospinal fluid from the brain into the circulatory system. In hydrocephalus condition the fluid builds up in the two large interconnecting chambers, and the brain and skull become enlarged because of the accumulation of the fluid. Hydrocephalus may be an acquired (caused by birth defects of the brain's drainage system, head injuries, tumors, parasitic or other infections) or congenital (present at birth). In young dogs, the presence of a dome-shaped head and/or non-closing, or persistent fontanel (also called fontanella) may indicate the development of hydrocephalus. Fontanel is a small gap between the incompletely formed cranial bones. Several such spots are usually present at birth and in most cases close usually by 3 or 4 months of age. In Chihuahua, the frontal fontanel, or molera, remains unclosed and this does not harm the dog. Signs of hydrocephalus include depression, severe loss of movement coordination, eye abnormalities, seizures, vision problems, and skull enlargement. Young affected puppies often show slow growth as compared to their littermates.
Demodicosis is an infestation with Demodectic mites that is characterized by skin lesions and alopecia. These mites are very common to dogs and are found in most healthy animals. The infestation is usually caused by immune system disorders, hypothyroidism, poor nutrition, cancer, and exposure to toxins. The generalized demodicosis is a serious skin disease that can take from 1 to 6 months to cure.
Cystinuria, a hereditary condition characterized by excessive urinary excretion of amino acids and formation of cystine crystals, which eventually leads to kidney and bladder stones. Chihuahua, Dalmatian, Dachshund, Tibetan Spaniel, and Basset Hound are genetically predisposed to cystinuria. Signs usually include blood in the urine, difficulty and pain in urinating, and small frequent amounts of urine. If a stone completely obstructs the urethra and thus blocks the outflow of urine (more common in male dogs) this may cause kidney failure, vomiting, and depression.
Mitral valve disease encompasses many heart problems involving degenerative thickening and progressive deformity of one or more heart valves, including mitral valve disease, mitral valve degeneration, mitral valve insufficiency etc. Mitral valve disease is a serious heart condition caused by the abnormal function of the valve that separates the upper and lower chamber of the left side of the heart. This disease is usually associated with heart murmur. It commonly affects the Miniature Schnauzer, Chihuahua, Fox Terrier, Cocker Spaniel, Cairn Terrier, Miniature Poodle, Bull Terrier, Boston Terrier, King Charles Spaniel, Miniature Pinscher, Dachshund, Doberman Pinscher, and Shetland Sheepdog. Males are 50 percent more likely than females to be affected. The diseases may result from congenital defect of the valve, defects in the muscles and tendons that operate the valve, or inflammation of the heart. The disease usually occurs in older dogs, however it is seen in young dogs and may result in premature death. Signs may include exercise intolerance, weakness, syncope (passing out), coughing at night or at rest because of a build-up of fluid in the lungs, shortness of breath, and lethargy. Mildly affected dogs can have a good quality of life for years. It all depends on when the diagnosis is made and when therapy is applied. There are many dogs with degenerative mitral disease that never progress to heart failure. While the prognosis for dogs with mitral valve disease at advanced stage is poor, some dogs may be managed with medications and low-sodium diet for a period that varies from case to case. There is no prevention for mitral valve disease. Early detection and appropriate treatment of the disease may improve the prognosis.
Hemophilia is a genetically inherited bleeding disorder caused by a deficiency of the blood clotting factors VIII (hemophilia A) or IX (hemophilia B). Classical hemophilia, hemophilia A, is the most common coagulation disorder in dogs. Signs of severe hemophilia usually include excessive bleeding from the gums, when getting adult teeth, and areas of bleeding under the skin in the regions of hind legs, the knee joint as well as the chest or abdomen (part of the body that encloses the stomach, intestines, liver and pancreas), forehead and he shoulder area, cough and lameness. Treatment may include periodic blood transfusions. The prognosis for dogs with severe hemophilia is poor since it usually results in lethal complications of the bleeding in the central nervous system. Dogs with a mild to moderate deficiency of the blood clotting factor, may survive to adulthood without showing signs severe enough to require veterinary attention.