Pregnancy And Lassa Fever Precautions

What is lassa fever?

Lassa fever is an acute viral haemorrhagic illness- ‘viral’ referring to it is caused by a virus, the Lassa virus; ‘haemorrhagic’ meaning it can cause internal bleeding; ‘acute’ meaning that the symptoms are time-limited, as opposed to ‘chronic’ symptoms which tend to last over long periods/can even be lifelong. Lassa fever can affect anyone from any age group.¹

The Lassa virus lives in rats, who are asymptomatic carriers (i.e. the rats themselves are not affected by the virus). They shed the virus in their urine and faeces. The infection can spread to humans if they come into contact with any item that is contaminated with the rats’ excrement-  for example by walking on floors that have rat urine or droppings. Diseases that can spread from animals to humans are called zoonotic diseases. 

Lassa fever can additionally be spread from person to person, usually via direct contact with contaminated body fluids such as saliva, semen or urine.²

In 80% of cases, Lassa fever is mild or asymptomatic, and the person will recover fully. In those who have symptoms, they generally appear gradually. The illness generally lasts between 6 and 21 days. Initial symptoms include fever (of up to 41℃), malaise (feeling unwell) and weakness. After a few days, symptoms such as headache, diarrhoea, cough and vomiting can occur. 

Lassa fever, in 1-3% of cases, is fatal due mainly to the occurrence of haemorrhages. Severe symptoms usually start in the second week of the illness.  Damage is caused to the blood vessels and consequently, there is bleeding within the vital organs including the skin, kidneys and liver. Other symptoms of severe cases include fluid build-up in the lungs, swelling of the head and neck, and seizures (fits).^1,3

Lassa fever occurs predominantly in West Africa and is endemic (i.e. spread throughout the country) in Sierra Leone, Nigeria, Guinea and Liberia. The type of rats that transmit the virus, known as Mastomys rats, live in these countries and will walk in and around people's homes, especially in rural settings.²

Lassa fever in pregnancy 

Pregnant people are particularly vulnerable to adverse outcomes of Lassa fever, especially those in the third trimester. This is because the virus has a high affinity for highly vascular tissues (meaning lots of blood vessels are present), such as the placenta and the developing foetus, which can be strongly affected by the infection. Pregnant people also have a significantly higher viral load, meaning the amount of virus found in the infected person’s blood is higher than those who are not pregnant. Adverse outcomes include maternal death, and/or death of the foetus (either miscarriage or stillbirth). Survival of Lassa fever in pregnancy is quite rare- with some sources quoting even up to 80% mortality during pregnancy and 90% in the perinatal period (meaning around the time of birth). Additionally, pregnancy is associated with the immune system of the pregnant person accommodating more so for the foetus rather than their own, making pregnant people even more susceptible.⁴

Diagnosis of Lassa fever in pregnancy is often challenging. Early-stage symptoms such as fever, malaise and tiredness can be from many different causes and do not necessarily point at Lassa fever directly. Other illnesses that cause haemorrhagic fevers such as malaria, Ebola and typhoid fever are present in West Africa and have similar early-stage symptoms. Therefore, diagnosis can only be confirmed by laboratory-based testing.¹ 

Part of the reason why pregnant people have poor outcomes is because of the lack of availability of hospitals in rural West Africa, and if the hospitals are there, they are poorly equipped and unable to proceed with the necessary diagnostic tests. For the milder flu-like symptoms that happen in the early stages, at-home treatment is frequent, only hospitalising the affected family member at a later stage, delaying diagnosis and favouring the progression of this condition. At this point, the patient’s life is at risk.

Management of lassa fever in pregnancy

Treatment for Lassa fever in pregnancy (and those who are not pregnant for that matter) is mostly supportive. Supportive care focuses on managing symptoms rather than treating the cause. This involves pain relief, rest and ensuring adequate hydration and nutrition. 

Ribavirin is a broad-spectrum antiviral drug that is often given to those with Lassa fever. However, its evidence base is conflicted, with some sources citing that it has improved clinical outcomes, especially if given in the early stages of the infection and others saying that there is not enough evidence to support its use for Lassa fever.⁴ According to UK NICE guidelines (a very widely used source of guidance for health professionals), ribavirin is contraindicated for those who are pregnant due to teratogenicity (meaning the drug can pass on from the pregnant person to the baby) and risk harm to the foetus. However, this evidence is based on animal studies and calls for more research to form a robust conclusion on its efficacy in pregnant patients.⁵ Conclusively, there is no evidence to suggest the efficacy of ribavirin as a prophylactic (preventative) measure against Lassa fever.²  

Additionally, there is no vaccine currently available to protect against Lassa fever, although they are being researched.²

Preventative measures against lassa fever

There can be various measures that individuals can take to prevent the spread and transmission of Lassa fever:

• Rodent control by families to avoid the rats coming into the house. This can be extended to rodent control within a community to reduce rats gallivanting around the area. Although having said this, the rats in the endemic areas are in large numbers, so it will not be possible to eliminate them entirely.² Having proper garbage disposal facilities far away from people’s homes is also important.
• Household hygiene is important: cleaning floors, storing food in closed containers away from rats, and avoiding consuming water and food that could be contaminated
• Personal hygiene like washing hands, washing clothes and protecting areas of broken skin are also important to prevent infection
• If a member of the household is infected, other family members should avoid contact as much as possible- especially with the body fluids of the infected person

Other measures that can be taken on a wider societal level include public education and awareness to know which preventative measures they can take, which symptoms to look out for and when to seek medical advice. This can involve health workers educating pregnant people since they are the most susceptible to severe outcomes. Lassa fever can be sexually transmitted, so education on safe sex is necessary too.  

It is also important for hospitals and clinics to have stringent infection control measures. Lassa fever is transmissible from person to person, therefore hospitals should be practising safe hygiene measures, proper disposal of contaminated equipment such as needles or personal protective equipment, and safe handling of samples eg. blood or urine samples of those infected so that other patients and staff are not exposed to the virus. However, Lassa fever mainly occurs in resource-poor areas where a “gold standard” level of infection control is unlikely. Hence, ensuring hospitals and healthcare workers have testing facilities and the equipment needed to diagnose and treat Lassa fever safety is an important precautionary measure. 

Ribavirin is often used for Lassa fever patients, although its evidence base, especially in pregnant people, is not robust. Therefore more research involving treatment strategies is necessary to improve outcomes for patients.⁶

Summary 

Lassa fever is a viral illness that predominantly affects West Africa. The Lassa virus is harboured by rats and can spread to humans through contact with the urine or faeces of infected rats. Most Lassa fever infections are either asymptomatic or result in mild symptoms. However, during pregnancy, particularly in the third trimester, an infection can be fatal for both, the foetus and the pregnant person. Therefore, it is crucial to be aware of the symptoms and take preventive measures, such as rodent control to prevent rats from entering homes. Additional precautions include public education campaigns and equipping hospitals to treat Lassa fever effectively. The current treatment strategy involves the drug Ribavirin, although its effectiveness remains controversial. This uncertainty highlights the need for further research into alternative treatments for this infection.