Mumps And Its Impact On Fertility In Males

Introduction

As many as 1 in 7 couples struggle to conceive due to fertility problems and it is estimated that up to fifty per cent is due to male infertility. A growing cause of concern with respect to male fertility is a resurgence of infections with the mumps virus, particularly affecting people born in the late 1990s to early 2000s, as this group may not have received the MMR vaccine as children. The MMR vaccine offers protection against not only mumps but also measles and rubella. 

Mumps is primarily an infection of the parotid gland (salivary glands) that is usually not harmful and passes after a week or two. However, the mumps virus can spread to other parts of the body, causing complications there. 

The testicles are the most common body part in which the mumps virus causes complications. For some young men, this can have a lasting impact on their fertility.¹ Therefore, understanding how mumps can cause these complications, and if they can be prevented, is a key area for medical research.

What is mumps?

Mumps is a viral infection that is spread just like a cold or respiratory infection – through droplets released when an infected person sneezes, coughs, speaks, spits or even breathes out. Droplets containing the mumps virus may infect a person by direct contact (such as being sneezed on), or indirectly through contaminated surfaces. 

Once in the body, the mumps virus infects the parotid glands. These are small glands in the face that produce saliva. Infection of these glands causes inflammation (parotitis), resulting in swelling just below the ears. This is commonly referred to as ‘hamster face’ and is characteristic of mumps infection.¹

Symptoms may also include:

• Headaches
• High temperature
• Joint and muscle pains
• Loss of appetite
• Feeling tired 

For the majority of people, a mumps infection will clear up in a week or two, and these symptoms will be mild and pass. However, in some cases, mumps can cause complications as a result of the mumps virus spreading to, and infecting, other parts of the body.¹ 

The most common complications are:

Rarer complications include temporary hearing loss (1 in 25 cases), permanent hearing loss (1 in 20,000 cases), and viral encephalitis –  infection of the brain tissue itself (1 in 1000 cases).

How common is mumps?

The MMR vaccine has significantly decreased the prevalence of mumps infections, and countries using a 2-dose vaccination schedule have shown a decrease in mumps cases by as much as 97%.² However, more recently, there have been outbreaks of mumps even amongst vaccinated individuals, particularly young adults. 

This does not mean that the MMR vaccine is ineffective, it is likely that without it mumps outbreaks would be more frequent, and those infected would suffer more severe symptoms and be at greater risk of complications. This was confirmed in a study, that showed that individuals who had previously had 2 doses of the MMR vaccine were less likely to show any complications, than people who had not been vaccinated or had had just one dose.³ However, the number of mumps outbreaks is increasing even in vaccinated individuals, suggesting the need for a third dose of the vaccine.

A more detailed look at mumps orchitis

Orchitis (inflammation of the testicles) is the most common complication of mumps in males who have been through puberty, affecting 1 in 3 individuals. This is often a painful swelling, usually restricted to one testicle but in a few cases affecting both testicles (10-30% of cases).^1,4 

Orchitis usually develops around a week after the initial swelling in the parotid glands. In some cases the epididymis (a small sperm-carrying tube connecting to the back of the testicle) can also become inflamed, causing further pain and discomfort. 

To diagnose mumps orchitis, a doctor may do a physical examination, a urine test to rule out any bacterial infections, or sometimes a testicular ultrasound scan. Laboratory testing of blood and/or saliva is needed to confirm a mumps infection.⁵

How does the mumps virus affect the testicles?

There is little research on mumps orchitis from human samples due to it being relatively uncommon and non-fatal. Therefore, most research currently uses mice as a model. One study showed that the mumps can infect nearly all testicular cell types in mice, including Sertoli and Leydig cells. 

Sertoli cells are important for ensuring the environment in the testicles is supportive of good-quality sperm production. Leydig cells are important for producing testosterone, which is essential for sperm production. It has been shown that testicular mumps infection results in high levels of proinflammatory proteins (cytokines and chemokines) being created, especially in the Sertoli cells. These chemokines attract immune cells to the testes, resulting in inflammation.⁵ 

The production of proinflammatory chemokines in Leydig cells disrupts testosterone synthesis by decreasing the production of an enzyme that is essential for making testosterone. Testosterone is essential for making sperm. 

Mumps orchitis can also cause testicular atrophy (degeneration of the testicle). This decrease in testicle size is reported in 30-50% of cases and is believed to be another way in which sperm production is altered.^4,6

How does this affect male fertility?

The inflammatory response in the testicles interferes with sperm production. The testes are usually an ‘immune-privileged’ organ, meaning the developing sperm cells are protected from your immune system. However, orchitis has been linked with disruption to the blood-testis barrier, which means that there is easier exchange of molecules, substances and cells between blood and testes. 

During spermatogenesis, antigens are created on the developing sperm cells. Usually, these sperm cells are protected from the body's immune cells, however, when the blood-testis barrier is disrupted, they lose their protection and may be targeted by immune cells, resulting in developing sperm cells being destroyed. As a result, a decrease in sperm count occurs. This is one way in which mumps orchitis affects fertility. Other seminal fluid abnormalities are also observed in mumps orchitis, including alterations in sperm morphology (shape) and motility (ability to swim).⁷ 

Some improvements in these abnormalities were observed in a study 6 months after mumps infection, whilst another study showed abnormal sperm qualities 3 years after mumps infection.^4,8 There is a large amount of variation between patients and relatively little research to determine an average time that these impacts on fertility persist.

Treatment and prevention

For most people, the mumps infection should clear up and symptoms subside within a week or 2 without treatment. There are currently no antiviral medicines recommended for treating mumps. However, orchitis can be painful and uncomfortable, but there are a few things you can do to relieve these symptoms:

• Taking pain relief medicines such as paracetamol and/or ibuprofen
• Wearing more supportive underwear
• Applying a warm or cold compress to the area¹

The MMR vaccine is very effective, 2 doses reduce the risk of becoming ill with mumps by 86%. However, outbreaks do still occur, even among the vaccinated population. 

To help prevent mumps from spreading, those infected should stay at home (at least for the first few days after the onset of symptoms) and maintain good hygiene. This includes regular hand washing and sneezing into tissues, then immediately disposing of them, because mumps spreads in a similar manner to respiratory viruses such as flu. You should always consult a healthcare professional if you are concerned, and not try to self-diagnose.

Summary

The MMR vaccine has been successful in reducing the spread of mumps infection, however, there have been recent outbreaks even in vaccinated people. Young adults are disproportionately represented among modern mumps cases and whilst for most people the infection is mild and clears within a fortnight, around 1 in 3 men develop symptoms in the testicles.

This includes pain and swelling, and there is evidence showing that this can cause both short and long-term impairments in fertility. This is because the inflammatory environment in the testicles interferes with sperm production. The impact of mumps orchitis on male fertility is a cause for concern, and more research is needed to ascertain the full extent to which mumps is related to fertility problems in men, and how these can be avoided.