The clinical presentation starts after 5-14 days from tick bite. The following system-wise presentation is seen in erlichiosis:
General Appearance: Patients with erlichiosis may present with confusion in 20% of cases and malaise due to the rapid destruction of the white blood cells in the system. The general feeling of being unwell may lower patient’s appetite leading to anorexia and vomiting because solid foods may not be tolerated at this time.
Head: Vascular headache may occur due to vasodilation of the temporal vessels from the systemic cytokine release. An immune mediated type of meningitis may ensue as one of HME’s complication may present as severe headache. Vascular fragility may manifest as petechial rash or maculo-papular rash of the face.
Abdomen: Enlargement of the abdomen may be evident with splenomegaly. The rapid cycling of white blood cells and lymph will lead to the enlargement of the spleen .
Extremities: A generalized feeling of myalgia of the muscles is one of the inaugural signs of HME and this is related to the generalized immune response. Intermittent muscular rigors may occur in the late stages of the disease.
The diagnosis of erlichiosis may be challenging because it may mimic several common viral disease in children and in adults. Presented with a patient having very high suspicion rate for erlichiosis with history of possible tick contact in endemic regions, it is medically prudent to check the entire body especially the hair part for the presence of the tick vector which is ardently removed.
The following laboratory tests are performed for patients with suspected erlichiosis afflictions:
In early erlichiosis, the prompt removal of tick vector from the host’s body may reverse the signs and symptoms of the disease arbitrarily. Physicians often prescribe doxycycline antibiotics for 7 to 10 days to address the infection in erlichiosis . Pregnant women may be given rifampin instead because doxycycline is contraindicated with pregnancy. Flouroquinolones may also be used with antipyretics during the early stages of HME.
The disease erlichiosis heralds a good prognosis with a healthy host and with prompt antibacterial treatment . The mortality rate in human monocytic erlichiosis is only 2% to 5%. Elderly patients beyond 60 years of age account for the majority of deaths encountered in HME . Majority of erlichiosis cases are generally asymptomatic or with mild symptoms like fever and malaise. HME carries a high hospitalization rate of 60%.
Erlichiosis poses a serious threat for those who are not treated promptly. Immuno-compromised patients may even have a higher risk for life threatening outcomes. The following serious complications may arise from HME:
Ehrlichiosis is caused by a Rickettsia type of bacteria called Ehrlichia that is generally transmitted in the United States by the bite of the Lone Star tick (Amblyomma americanum) in between mammalian hosts. Ehrlichia chaffeensis, Ehrlichia ewingii, and Ehrlichia muris-like may cause the disease.
A tick latches on the skin of a mammalian host where it gets its blood meal. They can either transmit the bacteria from their system or acquire it from its blood meal host. To effectively transmit the bacteria, the Lone Star tick requires at least 24 hours of latching on. Prompt removal of the transmitting tick may arrest the delivery of the bacterial load and prevent infection.
The incidence of erlichiosis in the United States abounds in states where there is direct contact of the mammalian host to the tick vector. Majority of cases in the US are distributed in the Texas, California and the eastern regions of the country . Studies suggest that erlichiosis is a seasonal disease that surfaces during the months of April to September . This tick-borne disease occurs worldwide mirroring the relative distribution of its vector and it close proximity to human hosts .
The bacteria Erlichia chaffeensis is an obligate, intra-cytoplasmic and gram negative organism that closely resembles Rickettsia spp. Erlichia thrives and multiplies within the monocytes vacuoles (pahgosomes) forming a large mulberry shaped aggregate referred to as morula. The defective monocyte and macrophage in HME renders the mammalian host’s immune system incapacitated. A widespread systemic response may be observable when the body’s immune system attacks this abnormal white blood cells and inclusion bodies.
Humans must reduce exposure in endemic areas to prevent contact with the vector. During camping trips, insect repellants must liberally be used to fend off the Lone star tick from latching on. Tucking one’s pants within the socks may reduce the tick’s point of entry to the skin. The regular self-examination for possible tick bites during outings is a prudent practice.
Erlichiosis generally resolves with the early introduction of appropriate antibiotics. Erlichiosis is an infection of the monocytes that may affect other mammals like dogs, sheep, cattle, horses and goats .
Diagnosis and Treatment
Patients who discover the tick in their skin must use fine tweezers to remove them being careful that the mouth parts left on the skin surface. The specimen must be placed on a covered jar on a moist cloth for future examination purposes when signs and symptoms occurs. Prompt medical attention must be given paramount priority when suspecting any tick-borne disease.