How to Test for Oral STDs

It is a common misconception amongst both men and women that oral sex (i.e. fellatio, cunnilingus, and analingus) is completely risk-free when it comes to infections. While oral intercourse is often thought to be a safer option compared to penetrative intercourse or conventional sex, the reality is that a variety of STDs can still be transmitted through direct contact with the mouth, lips, tongue or throat.

As such, it is important to monitor for symptoms of these infections as well as proactively test if there is a potential exposure risk, especially as a large proportion of these infections can be asymptomatic, or have symptoms that develop much later.

The most common infections transmissible through oral sex are Chlamydia, Gonorrhea, Herpes Simplex Virus (HSV), and Human Papillomavirus (HPV), and Syphilis. In this article, we will be outlining some of the common symptoms seen with these infections as well as how they can be tested.

Chlamydia and Gonorrhea

These are two of the most common STDs seen globally, and are caused by the bacteria Chlamydia Trachomatis and Neisseria Gonorrhea respectively. They will usually infect the genital region, urinary tract, anus, and oral cavity, although other sites of infection have been noted as well. While symptoms such as sore throat and throat discharge may be present in some individuals, up to 70-80% of throat infections with chlamydia and gonorrhea may be asymptomatic and a large portion will remain undiagnosed and untreated.

The most accurate method of testing for throat chlamydia and gonorrhea infections will be with Polymerase Chain Reaction, or PCR testing – this looks for specific genetic sequences from the DNA of these bacteria. Standard bacterial cultures are usually insufficient to pick up these infections.

Herpes Simplex Virus

There are two main types of HSV infection. Type 1 HSV is more commonly seen, and can be spread through both oral-to-oral transmission such as kissing, as well as oral-to-genital transmission. Type 2 HSV is more typically seen through genital-to-genital transmission, although it can also be spread to the mouth, tongue, and throat through oral sex. These viral infections can cause outbreaks of painful ulcers or cold sores at the site of transmission, and infection is carried lifelong. There is risk of transmission of these infections even without symptoms.

Testing for herpes infections can be performed either with blood serology testing or via PCR testing if there are symptomatic lesions. Serology or antibody testing will only be able to detect possible past exposure 1-3 months after transmission, and is not useful to detect new or acute infections.

Human Papillomavirus

HPV infections are one of the most common prevalent STDs worldwide. There are many subtypes of HPV, usually divided into low-risk and high-risk categories. Low-risk types include type 6 and 11, which are responsible for about 90% of genital warts or papillomas – these are benign, cauliflower-like growths on the skin and mucous membranes that can develop weeks to months after initial transmission. High-risk types include type 16, 18, 31, 33, 45 etc. and are more related to cancer risk, including cancers of the cervix, anus, penis, and mouth/throat. It is estimated that approximately 20,000 HPV-associated oral cancers are diagnosed per year in the US alone.

Warts from HPV are usually diagnosed clinically and do not require any specific testing; however, high-risk HPV infections are usually asymptomatic and would require PCR testing to be detected. Guidelines currently recommend women over the age of 30 to do regular HPV PCR testing together with their pap smears, and for men who have receptive anal sex to screen for rectal HPV if they are HIV positive. While oral HPV testing can be performed with the same type of test, there are no specific recommendations to do so, with the costs and benefits of the test to be determined by the individual and their doctor. HPV infections can be prevented with the HPV vaccine, which is now available for both males and females 9 years of age and older.

Syphilis

Syphilis infection is caused by the bacterium Treponema Pallidum. While incidence of syphilis had initially decreased with the availability of penicillin treatment in the 1940’s, rates of infection have been rising steadily for the past two decades, and it is commonly seen as a co-infection with Human Immunodeficiency Virus (HIV). Syphilis infection can be spread through direct contact to mucous membranes and compromised skin from an infected sore or chancre, usually at the genital region, anus, and mouth; it is estimated that around 20% of syphilis infections are transmitted through oral sex alone. Symptoms will depend on stage of infection at presentation, and can include sores or ulcers in primary syphilis, and a diffuse rash in secondary syphilis. Many cases are not detected when symptomatic and may be considered in the latent stage when screened on blood testing, or may even reach the tertiary stage many years after initial infection – this can cause complications with the heart and blood vessels (cardiovascular system), or with the central nervous system (neurosyphilis).

Syphilis testing is mostly performed with serological tests, which look for certain antibodies in the blood that can be detected 2-5 weeks after infection. Other forms of testing include dark-field microscopy, direct fluorescent antibody, and PCR testing; however, these are rarely performed in the clinical setting due to cost and availability of equipment and experienced lab personnel.

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