Introduction

Louse-borne relapsing fever (LBRF) is a disease caused by a type of bacteria (spirochete) called Borrelia recurrentis. This is a human-only disease that is spread by the body louse Pediculus humanus humanus. [1, 2] Spread occurs when the louse is crushed and the infected primary body cavity of the louse that contains infected circulatory fluid (known as the haemocoel) is released onto human skin. [3] Borrelia recurrentis then penetrates intact mucosa and skin to enter the blood stream. [2]

Geographical distribution

The geographical distribution of louse-borne relapsing fever has reduced due to better standards of living. In the past, major outbreaks of louse-borne relapsing fever occurred in Eurasia and Africa, but currently the disease is primarily found in north-eastern Africa with pockets of disease activity in Ethiopia but also in Somalia and Sudan. [4, 5-7]

An increase of asylum seekers from potentially LBRF-affected areas has been seen in the EU since 2014. [8, 9] The central Mediterranean migration route has been a major route for entering the EU for almost a decade, and over recent years migration flows along this route have increased substantially. This route has been used by various African nationalities, notably Eritreans, although the numbers of Syrians using this route has grown significantly in recent times. [10, 11]

Symptoms

The incubation period is usually between four and eight days (range: 2–15). The onset of symptoms is generally sudden as the spirochete starts to circulate in the blood stream. The symptoms include high-grade fever, chills and sweats, headache, meningism, muscle and joint aches and non-specific gastrointestinal symptoms such as nausea and vomiting. [1, 4]

Tests

The diagnostic test of choice is the direct identification of spirochetes in the blood by stained blood films (Giemsa), especially during the symptomatic, febrile phase. [6] Nucleic acid detection is carried out for species identification and to support the clinical diagnosis. [7] Malaria, typhoid fever, viral haemorrhagic fever, leptospirosis, typhus, tick-borne relapsing fever, non-typhoidal salmonellosis, meningococcal septicaemia and meningitis need to be considered in the differential diagnosis.

Detection of a clinical case should lead to source tracing and it is necessary to investigate and treat infected contact(s). Treatment of clothing for LBRF is necessary as infected lice can remain in the clothes. [2]

Treatment 

The disease can be severe and death occurs in 10% to 40% of untreated cases and in 2% to 5% of treated patients. The antibiotic of choice is doxycycline (tetracycline group), although other antibiotic treatments are also effective (penicillin G, erythromycin, chloramphenicol). [5] A potentially severe or fatal reaction to antibiotics can occur (the Jarisch–Herxheimer reaction).

More information can be found on the ECDC factsheet louse-borne relapsing fever.

Public health measures

Primary prevention of louse-borne relapsing fever relies on measures for avoiding infestation with body lice. Such infestations are linked with low socioeconomic status, over-crowding and poor personal hygiene.

Options to consider for the prevention and control of louse-borne relapsing fever include:

• Prevent overcrowding in reception centres for asylum seekers, as well as promoting and enabling adequate hygiene for asylum seekers;
• Raise awareness among asylum seekers, particularly at the point of entry into the EU, about lice infestation and possible louse-borne diseases;
• Check for signs of lice infestation during medical screening of asylum seekers and carrying-out delousing as required [12]. As the detection of infestation might not be very sensitive, preventive delousing can be considered;
• Source tracing and investigation of contacts of patients diagnosed with louse-borne relapsing fever, to identify other exposed persons and apply control measures and treatment in a timely manner;
• Monitor for the Jarisch–Herxheimer reaction when treating patients with louse-borne relapsing fever with antibiotics, which requires supportive care for monitoring fluid balance.

1. Fauci As, Braunwald E, Kasper DL, Hauser SL, Longo DL, Jameson JL, et al. Harrison's Principles of Internal Medicine, 17th Edition. 2008:2754.
2. Raoult D, Roux V. The body louse as a vector of reemerging human diseases. Clin Infect Dis. 1999 Oct;29(4):888-911.
3. Houhamdi L, Raoult D. Excretion of living Borrelia recurrentis in feces of infected human body lice. J Infect Dis. 2005 Jun 1;191(11):1898-906.
4. Cutler SJ, Abdissa A, Trape JF. New concepts for the old challenge of African relapsing fever borreliosis. Clinical Microbiology and Infection. 2009 May;15(5):400-6.
5. Elbir H, Raoult D, Drancourt M. Relapsing fever borreliae in Africa. Am J Trop Med Hyg. 2013 Aug;89(2):288-92.
6. Yimer M, Abera B, Mulu W, Bezabih B, Mohammed J. Prevalence and risk factors of louse-borne relapsing fever in high risk populations in Bahir Dar city Northwest, Ethiopia. BMC Res Notes. 2014;7:615.
7. Ramos JM, Malmierca E, Reyes F, Tesfamariam A. Results of a 10-year survey of louse-borne relapsing fever in southern Ethiopia: a decline in endemicity. Ann Trop Med Parasitol. 2008 Jul;102(5):467-9.
8. European Asylum Support Office. European Asylum Support Office. Newsletter - June 2015 2015. Available from: https://easo.europa.eu/wp-content/uploads/EASO-Newsletter-June-2015.pdf.
9. FRONTEX. Annual Risk Analysis 2015. Poland: Frontex, 2015. Available from http://frontex.europa.eu/assets/Publications/Risk_Analysis/Annual_Risk_Analysis_2015.pdf
10. European Commission. Questions and Answers: Smuggling of Migrants in Europe and the EU response [Internet]. European Commission; 2015 [cited 23 July 2015]. Available from:  http://europa.eu/rapid/press- release_MEMO-15-3261_en.htm.
11. Interactive Map on Migration. 2014 MTM Map on Mixed Migration Routes in the MTM Region [Internet]. 2014 [cited 23 July 2015]. Available from:  http://www.imap- migration.org/index.php?id=470&L=3%27A%3D0.
12. Centers for Disease Control and Prevention. Body lice – Frequently asked questions [Internet]. CDC; 2013 [cited 14 September 2015]. Available from http://www.cdc.gov/parasites/lice/body/gen_info/faqs.html