- Since 2007 all puppies are screened under the Australian Canine Eye Scheme (ACES) at 6-7 weeks old.
- Breeding stock is re-tested under the ACES between 3-6 years old
- Breeding stock is re-tested under the ACES after the dog has reached 9 years old
- Commencing 2013 all breeding stock is DNA tested for PRA-BJ1 before breeding or must be Normal by Parentage History for the disease.
Dogs with the following results may be bred
- Normal eyes
- Minor iris to iris or minor floating PPM (of no clinical significance)
- Carriers of Affecteds of PRA-BJ1 may only be bred to a Basenji that is Normal.
Dogs with the following may not be bred
- Dogs with iris to lens or iris to cornea PPM
- Dogs with any degree of coloboma
- The following combinations of PRA-BJ1 – carrier x carrier, carrier x affected and affected x affected.
- PRA – affected on physical examination
- Dogs affected with Corneal Dystrophy – Endothelial
The eye is a delicate yet durable organ. They eye consists of several layers; the cornea is transparent and covers the front of the eye. The iris is the coloured part the iris is responsible for letting more or less light into the eye. The lens gathers and ‘bends; the light in order to focus it on the retina, the retinal converts the light into signals which are sent, via the optic nerve to the brain. The large area between the lens and the retina is filled with a jelly -like fluid known as the vitreous. The vitreous provides nutrients and removes waste products it also gives the eye its shape.
Persistent Pupillary Membrane (PPM)
Persistent Pupillary Membrane (PPM) is a common condition found in Basenjis. During development and whilst in the uterus the pupillary membrane covers the puppies pupil. The purpose of this membrane is to supply blood to the developing lens. Normally the pupillary membrane will disappear or will be absorbed shortly after birth, the absorption of the membrane may not be completed when puppies first open their eyes but in most dog breeds remnants of the membrane disappear by the time the pup is 4-5 weeks old. In the case of many Basenjis tiny remnants of the membrane persist or remain and these become PPM’s.
There are several forms of PPM; the least significant are iris to iris and floating PPM’s. Iris to iris PPM’s span across the pupil. They may be single strands or forked. This type of PPM may become less prominent or even completely disappear as the puppy gets older. Floating PPM’s are strands that are attached to the iris at one end the other end floats free. Both minor iris to iris and minor floating PPM are generally considered to be of no clinical significance and will not cause any vision impairment. More significant is Iris to lens PPM’s these PPM’s can cause opacities or cataracts at the point where they attach to the lens. Although these cataracts do not usually progress they can, in some cases, cause some minor vision impairment. More significant again is Iris to Cornea PPM’s, these strands cause opacities to the cornea, they may be small or severe. Some improvement may be seen as the puppy gets older. The strands may regress but will probably not completely disappear. Puppies severely affected with numerous strands may be blind.
PPM in Basenjis is almost certainly hereditary but the mode of inheritance is unknown. Previously, in America, the Canine Eye Registration Foundation (CERF) did not certify dogs with PPM, however, due to work done by breeders in that country to decrease the occurrence and severity of PPM, Basenjis that have minor iris to iris PPM can now quality for a CERF certificate. In Australia a Basenji tested under the Australian Canine Eye Scheme (ACES) found to have just one minute PPM strand will be diagnosed as being affected.
PRA is a complex disease. It is an inherited disease of the retina. The retina is the layer of the eye that receives light which is gathered and focused by other eye components. The retina converts the light into electrical signals that are sent via the optic nerve to the brain. The retina contains photoreceptors called rods and cones; rods help the dog see in the dark and cones help to establish certain colours.
There are different forms of PRA; inheritance ‘type’ (recessive/dominant) and age of onset etc. Some breeds experience early onset. Basenjis tend to experience late onset PRA which is unfortunate as there is a potential that affected animals have been bred before clinical diagnosis. Normally dogs will show signs of degeneration of the retina between 1 and 8 years of age. In most breeds PRA is recessively inherited but there are some exceptions where it is dominantly inherited or even sex-linked; in Siberian Huskies PRA is primarily found in males.
Normally the first symptom noticed is as a result of the pupils dilating – a ‘glow’ or increased ‘eye shine’ is often noticed. At this point it may also be noticed that the dog appears to have difficulty seeing in the dark/dusk – ‘night blind’. Night blindness is due to the degeneration of the ‘rod’ photoreceptors. It is normally accepted that a dog with PRA will eventually go blind. The degeneration normally atkes 12 months or less from diagnosis.
There is no cure for PRA, however progression of the disease cane be slowed by nutrition; antioxidant supplementation can slow down the deterioration of the retina. An eye exam by a registered Ophthalmologist will diagnose the disease however the exam cannot predict whether the dog will develop the disease later in life.
Research Link: http://www.molvis.org/molvis/v19/1871/mv-v19-1871….
With this condition white or grey spots are seen in the eye and can be associated with cholesterol or fatty deposits in the cornea. This condition is not uncommon in Basenjis. It generally does not cause any vision impairment at all.
A condition when the cornea takes in too much fluid, which clouds the cornea and negatively affects vision. This condition is fairly rare in Basenjis but is known to worsen in the offspring if both sire and dam are affected.