Vector-Borne Tularemia: A Re-Emerging Cause of Cervical Lymphadenopathy

Abstract

Tularemia is a zoonosis caused by the highly invasive bacterium Francisella tularensis. It is transmitted to humans by direct contact with infected animals or by vectors, such as ticks, mosquitos, and flies. Even though it is well-known as a tick-borne disease, it is usually not immediately recognised after a tick bite. In Slovenia, tularemia is rare, with 1-3 cases reported annually; however, the incidence seems to be increasing. Ulceroglandular tularemia is one of its most common forms, with cervical colliquative lymphadenopathy as a frequent manifestation. The diagnosis of tularemia largely relies on epidemiological information, clinical examination, imaging, and molecular studies. Physicians should consider this disease a differential diagnosis for a neck mass, especially after a tick bite, as its management significantly differs from that of other causes. Tularemia-associated lymphadenitis is treated with antibiotics and surgical drainage of the colliquated lymph nodes. Additionally, tularemia should be noted for its potential use in bioterrorism on behalf of the causative agents' low infectious dose, possible aerosol formation, no effective vaccine at disposal, and the ability to produce severe disease. This article reviews the recent literature on tularemia and presents a case of an adult male with tick-borne cervical ulceroglandular tularemia.

Keywords: bioterrorism; lymph node excision; lymph nodes; serology; ticks; vector-borne diseases.

Figure 2

Cervical lymphadenopathy in a patient with ulceroglandular tularemia. A fluctuating neck mass is seen over the right sternocleidomastoid muscle (blue arrow), a superficial scab near the neck mass—a possible tick bite location and bacteria entry site (red arrow)—and enlarged supraclavicular lymph nodes on the right side (black arrow). Blue and red arrows anatomically correspond to Figure 1A–C and a black arrow to Figure 1D.

Figure 1

Ultrasonographic neck evaluation of the patient with ulceroglandular tularemia. (A) The hypoechoic area of 5 cm × 1 cm × 2 cm (green lines) corresponds to inflammatory changes in subcutaneous fat involving the platysma muscle (PM) above the sternocleidomastoid muscle (SCM) with abnormal adherent lymph node (LN); (B) Doppler ultrasonography shows the absence of blood flow in liquid-filled structures above SCM, which corresponds to partly colliquated abnormal lymph nodes (green line) and a non-compressible arterial flow under SCM, which corresponds to the carotid artery (CA); (C) a conglomerate of abnormal partially colliquated lymph nodes (green line) above SCM; (D) a conglomerate of abnormal 40 mm × 7 mm large supraclavicular lymph nodes overlying the intercostal space (ICS). Panels (A–C) anatomically correspond to a blue and red arrow in Figure 2. Panel (D) anatomically corresponds to the black arrow in Figure 2.