Sexually transmitted infections (STIs) affect millions globally. These infections can be caused by various pathogens, including bacteria, viruses, and parasites. Understanding parasitic STIs is important for prevention and management.
Understanding Parasitic Infections
Parasites are organisms that live on or in a host, obtaining nutrients at the host’s expense. Parasites differ from bacteria and viruses as they are typically larger, ranging from single-celled protozoa to multicellular insects and mites. Some parasites can be visible to the naked eye. Parasitic STIs are primarily transmitted through intimate physical contact, such as sexual activity.
Common Parasitic STDs
Trichomoniasis
Trichomoniasis is a common STI caused by a single-celled protozoan parasite, Trichomonas vaginalis. It primarily infects the lower genital tract, including the vagina and urethra. Many individuals, especially men, experience no symptoms, but some may develop irritation, discharge, or painful urination.
The infection is primarily transmitted through sexual intercourse. Globally, there are an estimated 156 million new cases annually, making it the most common curable STI worldwide. In the United States, approximately 2 million infections were estimated in 2018.
Pubic Lice
Pubic lice, also known as “crabs,” are tiny parasitic insects (Phthirus pubis) that infest coarse body hair in the pubic area. These yellowish-grey or red insects resemble tiny crabs. The main symptom is intense itching in the affected areas, which often worsens at night. Visible nits (lice eggs) or the lice themselves may be present on the hair shafts.
Transmission primarily occurs through close physical contact, most commonly during sexual activity. Sharing personal items like bedding, towels, or clothing can also lead to transmission. Pubic lice do not burrow into the skin but feed on human blood, causing the itching.
Scabies
Scabies is a contagious skin condition caused by the microscopic mite, Sarcoptes scabiei. These mites burrow into the superficial layers of the skin, where they live and lay eggs. The most prominent symptom is intense itching, particularly at night, which can disrupt sleep.
A rash typically appears, which can look like small red, brown, or gray bumps, and thin, wavy lines or “burrows” may be visible on the skin surface, especially in skin folds. Scabies is transmitted through prolonged skin-to-skin contact, often occurring during sexual activity. It can also spread through shared infested items, such as bedding or clothing.
Diagnosis and Treatment Approaches
Diagnosing parasitic STIs involves a clinical evaluation, including patient history and physical examination. For trichomoniasis, a healthcare provider may perform a microscopic examination of a genital sample, known as a “wet mount,” to identify the parasite. Nucleic acid amplification tests (NAATs) also offer sensitive detection for trichomoniasis. In cases of suspected pubic lice or scabies, visual identification of the parasites, their eggs, or characteristic burrows on the skin aids in diagnosis.
Once diagnosed, parasitic STIs are treatable with specific medications. Trichomoniasis is typically treated with oral antibiotics. Pubic lice and scabies are commonly treated with topical creams or shampoos. All sexual partners of an infected individual should also receive testing and treatment to prevent reinfection and spread.
Prevention and When to Seek Medical Care
Preventing parasitic STIs involves practicing safer sex, including consistent and correct condom use. Avoiding the sharing of personal items like towels, bedding, or clothing also reduces the risk of transmission for pubic lice and scabies. Open communication with sexual partners about sexual health and STI status is also important.
Seek medical attention if STI symptoms appear, such as unusual discharge, itching, or rashes in the genital area. Seeking care after unprotected sexual contact or for routine STI screening, especially if sexually active with multiple partners, is recommended. Prompt diagnosis and treatment are important for managing the infection and preventing its transmission to others.