Lyme disease: An important Zoonotic disease transmitted through Tick Bite
August 22nd, 2017 | Rana Hamid Ali Nisar | No Comments
Climate change is a burning issue nowadays as temperature and humidity of earth is rapidly increasing day by day which provides a suitable environment for vectors (ticks, mosquitoes, mites, fleas, lice) to survive and reproduce rapidly. As a result of climate change, there is an increase in rainfall which in return favors the transmission of vector-borne diseases by providing more breeding sites. As a result of increased rainfall chances of floods are also increased which facilitate vectors in their survival. Lyme disease is very important zoonotic disease and is caused by bacteria transmitted by vector ticks of ixodes genus which attack the animal for blood feeding. Symptoms include fever, migraine, tiredness, and specific skin rashes known as erythema migrans (expanding areas of redness). About 25-50 percent of infected people do not develop a rash. If disease is not treated on time then infection may spread to heart, joints and nervous system.
How is Lyme disease transmitted?
It is a disease of zoonotic importance. Small mammals and birds are natural hosts and ticks that feed on this host are responsible for the transmission of disease. Hard bodied ticks of genus ixodes are main vector of Lyme disease. Nymphal stages are more dangerous as compared to larval stages because they are small (less than 2mm) and feed for longer period of time undetected. They feed during spring and summer months. Adult ticks also responsible for transmission of disease but due to their larger size they are easily seen with naked eye and removed before they transmit bacteria. The tick must be attached for 36-48 hours or more before the bacteria can be transmitted. Person to person transmission is not reported yet. During pregnancy, there may be chances of placental infection but no negative effects found in the fetus. Lyme disease is not transmitted through air, food, water and from the bites of fleas, mites, mosquitoes. Ticks not known to cause Lyme disease are Amblyomma americanum, Dermacentor variabilis, Dermacentor andersoni, and Rhipicephalus sanguineus.
Signs and symptoms of Lyme disease:
Lyme disease can affect multiple body systems. Not all the patients with this disease show all clinical signs. Incubation period ranges from one to two weeks to months. There is 2 type of signs. Early signs which can be seen from three to thirty days after the bite of tick. These include fever, migraine, chills, joint and muscle pain, tiredness, and swelling of lymph nodes. Erythema migrans rashes are specific for Lyme disease and these can be seen in every part of the body and may begin at the site of tick bite and may feel warm to touch but not itchy and painful. Another type of signs can be seen days to months after the tick bite and in this case sign and symptoms are severe headaches, neck stiffness, arthritis with severe joint pain and swelling, facial palsy, nerve pain, irregular heartbeat, dizziness, inflammation of brain and spinal cord, short-term memory loss.
Epidemiology of Lyme disease:
Lyme disease was first documented in 1976. Nowadays it is most commonly reported tick-borne disease in USA. Lyme disease also reported in Europe, Japan, and China. People living in heavily wooded areas are most affected. Lyme disease is transmitted by 4 spp of Ixodes worldwide, Ixodes scapularis in the north central US and northeastern, I. ricinus in Europe, I. pacificus in the western US, and I. persulcatus in Asia
How to Diagnose the Lyme disease:
Borellia is very difficult to culture in laboratory. To diagnosis Lyme disease clinical sign & symptoms are very important. History of a tick bite is an important tool to diagnose the disease. Additionally, some serological tests are also used to diagnose the disease. Among serological tests, ELISA and Western blot are most commonly used. PCR is also used to detect the genetic material of Lyme disease spirochete. To perform serological and molecular test blood and CSF (cerebrospinal spinal fluid) is used.
Differential diagnosis of Lyme disease:
Differential diagnosis can be made from Cellulitis, Bell Palsy, Chronic Fatigue Syndrome, Pediatric Contact Dermatitis, Insect bites, Myocarditis, and other tick borne-diseases.
Treatment of the Lyme disease:
Antibiotics are primary treatment. In early infection, doxycycline is recommended orally because doxycycline successfully treats Borrelia bacteria and also many infections caused by the bite of tick. Use of Doxycycline should be avoided in children younger than 8 years of age and in pregnant women. Replacement of doxycycline is azithromycin, ceftriaxone, and amoxicillin. Treatment usually continues for one to four weeks. If swelling of joints persists then the second round of treatment may be necessary.
How to prevent Lyme disease:
Protective clothing includes hat, long sleeve shirt, and long pants help to prevent tick bites. Light color clothes make the tick easily visible before it attaches itself. Pets are a source of bringing ticks from outside into the house so special care should be taken while handling pets. Permethrin spray is widely used to control ticks but according to CDC only DEET (diethyltoluamide) is effective at repelling ticks. Lyme disease is also prevented by management of host animals. If we reduce the host mammals on which adult ticks depends for feeding and reproduction then tick population is reduced significantly.
Control of Lyme disease:
Control of disease can be done through control of vector transmitting disease. For this purpose acaricide spray during tick season especially early summer for nymph control and during winter to control the adults. Different types of formulations are available in the market in the form of dips, sprays, pour-ons, spot-ons, dust, and injectable.
Tick removal is very important to reduce the transmission of Lyme disease as removal within 36 hours can reduce the transmission rate. Best method to remove tick is simply pulled the tick out with the help of forceps near to the skin as, without crushing the body of tick.
Vaccination of Lyme disease:
Recombinant vaccine is available against Lyme disease. Vaccine based on outer surface protein An of B. burgdorferi. In clinical trials, this vaccine confers protective immunity to Borellia with only mild and transient adverse effects. Vaccine available in market as LYMErix and on basis of clinical trials approved by FDA (Food and Drug Administration) on December 21, 1998. Despite approval by FDA, the use of vaccine is limited because of many reasons including its cost and some vaccine recipients developed some autoimmune side effects.
Control measures to prevent zoonosis:
Control measures to prevent human population from transmission of zoonotic diseases include:
Special care during the summer season as ticks and other arthropods are more prevalent during summer. In lush green areas with high bushes and leaf litter on the ground should be avoided by walking on clear trails. Repellents should be used on naked skin to keep ticks away from body. While applying any repellent extra care should be taken and avoid sensitive parts like eyes, mouth, etc. Apply solution containing Permethrin 0.5% on boots, socks, tents, and pants. People having pets in their houses and farm should take great care of their pets especially dogs because ticks may travel from dogs to other farm animals and humans. Different kinds of acaroids are available for pets in the form of impregnated collars, pour-ons, sprays, injectable, and dust. Some acaroids acts on contact with body and kill the ticks while some acts by absorbing into blood of the animal to kill ticks. Ivermectin, Amitraz, Fipronil are examples of such kind of products.
This article is collectively authored by Rana Hamid Ali Nisar1, Dr. Muhammad Sohail Sajid1,2, Prof. Dr. Zafar Iqbal1. 1Department of Parasitology, 2One Health Laboratory, US-Pakistan Center for Advanced Studies in Agriculture and Food Security (USPCAS-AFS), University of Agriculture, Faisalabad, Pakistan.
Short Link: http://www.technologytimes.pk/?p=17983