Use of Artificial Insemination in Koalas

Artificial Insemination (AI) is used commonly in domestic species but is just recently beginning to be applied to conservation efforts of exotic species. While AI has not produced viable young in most marsupials, it has emerged as a significant reproductive tool in the Koala species. Use of AI in koalas has successfully produced viable young in the pouch, and is now considered an import tool for conservation.  In koalas, semen is collected via electroejaculation or through use of an Artificial Vagina, and frozen semen is utilized for insemination.

Artificial Insemination has numerous benefits. Currently, it is widely used in captive populations as well as minimally in fragmented wild populations. Fragmented wild populations are at similar risk as captive populations to decreased genetic diversity and inbreeding. Artificial insemination allows the influx of new, viable genes into an otherwise isolated populations and facilitates genetic exchange nationally and internationally. In addition, the use of AI to produce viable young is more cost effective and safer than the transport of live animals for breeding.

However, certain concerns must be taken into account with the use of AI. Chlamydia has been found in the ejaculate of koalas who demonstrate clinical reproductive disease. As a result, research has shown that Chlamydia can be transmitted via contaminated semen. Semen must be screened or cleared of infection prior to insemination.

Screening and Treating Ejaculate prior to Insemination

Much research has been conducted in the search for screening protocols or treatment of infected semen. Screening of semen is done through a PCR assay which detects Chlamydia particles in the ejaculate.

Treatment of infected semen with antibiotics prior to insemination is a more complex process than a simple PCR screening. However, successful treatment of infected ejaculate allows an infected but genetically valuable animal to contribute to the gene pool. As such, treatment methods of semen have been a furious area of research in recent years.

In one recent study (Bodetti et.all), semen was collected from seven mature and healthy koalas. Viable Chlamydia pecorum was added to the ejaculate and incubated. The semen was then divided up into control samples (for each ejaculate) as well as different aliquots for antibiotic treatment. The study tested penicillin, erythromycin, tetracycline and streptomycin for both effectiveness at inactivating the Chlamydia bacteria as well as the antibiotic’s effect on motility and viability of the sperm. The results are summarized in the following table.

*Penicillin was found to be toxic to sperm in previous work (Johnston, S. et.all)

Clearly, the use of certain antibiotics in ejaculated semen can deactivate Chlamydia while maintaining viable semen for insemination. It should be noted that erythromycin causes significant damage to the sperm plasma membrane, making sperm unsuitable for insemination. In contrast, tetracycline inactivates Chlamydia and shows no adverse effects on spermatozoa. However, if given systemically, tetracycline causes significant weight loss and potential mortality. In addition, previous research has demonstrated that administration of antibiotics in vivo does not eliminate the presence of viable Chlamydia from koala ejaculate. As a result, use of antibiotics should be considered an important management tool for treatment of koala ejaculate prior to insemination, but not for use systemically.  In addition, because treatment with the correct antibiotic doesn’t adversely affect sperm, koala semen could potentially be treated before insemination without prior screening for Chlamydia.

Development of a Vaccine