Infectious agents can impair various important human functions, including reproduction. Bacteria, fungi, viruses and parasites can interfere with the reproductive function in both sexes, most of which are sexually transmitted. Infections of male genito-urinary tract account for about 15% of the cases of male infertility. Infections can affect different sites of the male reproductive tract, such as the testis, epididymis and male accessory sex glands. Spermatozoa themselves subsequently can be affected by urogenital infections at different levels of their development, maturation and transport. Infections affecting reproductive organs in women are collectively referred to as Pelvic inflammatory disease ( PID). Infections are a major threat to women who are trying to conceive. Many genital tract infections can cause infertility by blocking fallopian tubes. Infection of the endometrium (endometritis) creates a hostile environment for embryos to implant causing infertility. Infection of ovaries (oophoritis) can alter the quality of eggs leading to infertility.

Common infections causing infertility are:

Chlamydia is the most common sexually transmitted bacterial infection (STI) associated with male infertility, affecting millions of people every year. Symptoms of an active infection may include a burning sensation during urination, a light-coloured discharge from the penis, and tender/swollen testicles. It is important to note that up to half of infections do not produce noticeable symptoms. An uncontrolled infection by Chlamydia can cause permanent scarring and blockages of the ejaculatory duct (epididymitis) or may impair sperm production (orchitis). In women, chlamydia can spread to the upper genital tract (uterus, fallopian tubes and ovaries) resulting in PID and the possibility of ectopic pregnancy or infertility. It can also cause inflammation of the cervix, resulting in challenges in conceiving by affecting the cervical mucus. It is often asymptomatic and causes damage to the tubes much before diagnosis.

Gonorrhoea is an STI commonly associated with male infertility. Symptoms of an active infection may include a burning sensation during urination and a darker-coloured discharge from the penis. Similar to Chlamydia, gonorrhoea may also cause permanent scarring and blockage of the ejaculatory duct or damage sperm production. Females infected with this bacterial infection have a 10 – 20% risk of developing infertility. Symptoms include dysuria, dyspareunia, lower abdominal pain, purulent and foul-smelling discharge from the vagina. Gonorrhoea damages tubes and causes sloughing, thereby infertility.

Common infection of childhood presenting as swollen lymph nodes under the jawline caused by an airborne virus. Men infected with mumps after puberty can suffer from painfully swollen testicles and can have permanently impaired sperm production.

Tuberculosis is a significant cause of infertility in developing countries, particularly in India. It’s a bacterial infection known to attack the reproductive system and cause permanent tubal blockages in both men and women. Genital TB is usually secondary to TB elsewhere in the body. Genital TB is often symptomless, presenting as only infertility. The cause of infertility is usually due to damaged/ blocked tubes, tubo- ovarian mass, endometritis and adhesions in the pelvic cavity.

Mycoplasma is an extremely tiny, sexually transmitted bacteria that can latch onto sperm cells and reduce their motility. Infection with Mycoplasma typically does not produce noticeable outward symptoms but may be diagnosed by culturing the semen. In women, it causes non-specific tubal changes causing salpingitis. Due to inflammation of tubes, sperm motility in the tube is affected and also creates a hostile environment for the gametes.

Non-sexually transmitted urinary tract infections are relatively rare in men but can occur. In these cases, most of the damage to fertility is caused by the entry of white blood cells or “leukocytes” to fight the bacteria. The leukocytes release toxic substances to kill the bacteria that can cause collateral damage to sperm. These types of infections are often discovered by the presence of large numbers of leukocytes during a semen analysis. If the infection is treated with antibiotics, full fertility can typically be restored. Early diagnosis and treatment is the key to preventing damage to reproductive organs. Since many of these infections do the damage much before diagnosis, prevention is the best approach to avoid fertility-related issues.