The Importance of Genetic & Color Diversity
Positive Path Forward - After a Dire Warning
Fortunately, my cat breeding journey stated in 2020 with a pair of genetically diverse Thai Burmese cats. This pair of cats were the product of decades of hard work and dedication from The International Maew Boran Association (TIMBA) in Thailand and Dr. Schar of Indian Spring Cats. My family and friends were mesmerized by the personality, beauty and health of my cats and kittens. These cats were clearly the ultimate companions.
Thai Burmese, Tonkinese and Siamese are cats that have recent parentage from Thailand based on genetically diverse Thai cats. Many countries have organizations that provide cat shows and cat registries that often have very specific aesthetic, color and ancestry rules. We are currently in the process of registering with TIMBA. We chose TIMBA since the organizations that register cats in the U.S. have rules that do not allow for the color and genetic diversity to the extent recommended by the leading cat researchers. However, we are open to registering with the U.S. based cat organizations if the registration rules were updated to include more colors as detailed in the Tamra Maew and to allow a greater number of genetic outcross cats from Thailand. The Tamra Maew is one of the oldest examples of a breed standard and includes many of the Thai cat coat colors historically found in Thailand.
History of the Burmese Genetic Scientific Studies
A warning was issued for the American Burmese breeders at the turn of the 21th century that there was trouble brewing with the breed.
In January 2008, an article entitled “The ascent of cat breeds: Genetic evaluations of breeds and worldwide random-bred populations” was published in the journal Genomics and presented data that registered Burmese cats were some of the most inbred cats in the world.
The minutes from the The International Cat Association meeting in Spring 2011 in Harlingen, Texas, contain a warning from Dr. Leslie Lyons: “…Burmese (have) one of the highest levels of inbreeding and lowest levels of genetic variation. Burmese were established in the post-World War II breed bloom, and has been a moderately popular breed. However, concerns for two diseases, a craniofacial defect and hypokalemia, has limited migration of cats between countries and within the USA, and fractionation of the breeding pool by color preferences within the USA has also caused poor breeding dynamics”
It became a very sad situation with some American Burmese cat breeders experiencing the results of inbreeding: small litter size, high kitten fatality rates, defects and deformities, poor immunity, and physical abnormalities. Fortunately, some cat breeders such as Dr. Schar of Indian Spring cats, decided to invest in the daunting task of increasing the genetic diversity of the Burmese cats in America. You can read about Dr. Schar’s journey here.
All our breeding cats have parents, grandparents or other ancestors imported through TIMBA from Thailand and come from Dr. Schar’s genetic improvement program. He gave an update on his program in 2020 here.
Dr. Leslie Lyons Note from June 27, 2016
Below is a note from Dr. Leslie Lyons from one of Dr. Schar’s articles. I bolded the most relevant recommendations that I use in my program.
Genetic Notes on the Burmese Cat Breed
27 June 2016
The Feline Genetics Laboratory, formerly of the University of California – Davis (UC Davis), now at the University of Missouri, has had long associations with Burmese breeders and veterinary researchers to define and identify the genetic mutations that cause various maladies in the Burmese breed. Many published studies (several listed below) have demonstrated that the Burmese breed has many genetic conditions, although the prevalence of these conditions is variable between countries. The Burmese in the USA are historically known for the autosomal recessive craniofacial defect that developed from the Contemporary lines of USA Burmese. Burmese carrying this condition have been identified in the UK, Europe and Australia due to the importation and use of the Contemporary lines. In addition, any other breed that has outcrossed to Contemporary Burmese has risk of the craniofacial defect. Recently, American Burmese breeders may be pursuing an organized project for heart disease.
In contrast, non - American Burmese are afflicted with several other conditions including GM2 gangliosidosis, hypokalemia, oral facial pain, diabetes, high triglycerides, a mid- line closure defect, and dermatosparaxis (stretchy skin, cutaneous asthenia, Ehlors- Danlos Syndrome). The genetic mutations for hypokalemia and GM2 gangliosidosis have been identified and like the craniofacial defect, the genetic test is available to assist breed management. Genetics studies regarding oral facial pain, diabetes, high triglycerides, flat-chested kittens, and dermatosparaxis are underway by our laboratory, in collaboration with other researchers, and independently by other researchers.
Our genetic studies have also included examining the population genetics of the different cat breeds and worldwide populations. In 2007, we published the first breed study that demonstrated that Singapura, Burmese and Birman had the lowest genetic diversity of the cat breeds we examined. A study between Singapura breeders and the UC Davis Veterinary Genetics Laboratory (VGL) supported our findings. Our recent studies demonstrate that the non-USA Burmese has as low genetic variation as the USA lines of Burmese. We strongly recommended outcrossing for all the Burmese breeds, including USA and non-USA Burmese.
Based on genetics, the Burmese breed originated from cats of Southeast Asia. Our genetic studies group cats from Thailand, Cambodia, Vietnam, Brunei and the Philippines as Southeast Asia cats. Historically, Burmese are considered to have origins from Thailand. Thus, random bred cats from Thailand and perhaps other regions of Southeast Asia are recommended as strong genetic candidates for outcrossing. Genetic tests for colors and health conditions can assist the selection of cats that may be the most advantageous for outcrossing. Other breeds with Southeast origins would also be of value to the Burmese outcrossing program, including Singapura, Bombay, and Burmese from any country. Burmilla and Asian have been crossed with Persian cats, which have western origins, thus, the use of these recent crossbred breed cats would add significant diversity, but of a different “racial” origins. Other Southeast Asian breeds include Siamese (and its breed derivatives), Korat, and Birman.
Because of our various genetic projects that include Burmese from different countries, we have been able to compare the genetics of the Burmese breed groups regionally. USA Burmese have high homozygosity (0.38), implying low genetic diversity (See attached report). The non-USA Burmese, which is a mixture of UK and Australian Burmese also have low diversity and high homozygosity (0.41), as compared to random bred cats (0.04) and other breeds. When we examine the Burmese diversity by plotting the genetic differences (termed multi-dimensional scaling (MDS), we find that the USA and non-USA Burmese do not cluster together and form independent genetic groups. The USA cats have a larger spread to their cluster as it includes Contemporary and Traditional lines of Burmese. Thus, Burmese breeders may consider crossing the Burmese cats from different countries to help improve genetic diversity.
Other genetic conditions in Southeast Asian cats include different forms of gangliosidosis in Korat and Siamese cats and pyruvate kinase deficiency in Singapura. Some Birman lines may have a susceptibility to FIP.
Overall, we have more genetic projects concerning Burmese than for any other breed and our various genetic studies have repeatedly demonstrated that Burmese, regardless of country, have amongst the lowest genetic diversity of all cat breeds. An organized and multi-faceted outcrossing program for the breed is highly recommended which includes the use of genetic testing and outcrossing to different populations and breeds.
Best regards,
Leslie A. Lyons, PhD