Pathophysiology Of The Bubonic Plague - Term Paper Example

?Bubonic Plague Overview Plague is a disease caused due to infection with Yersinia pestis. It is a zoonotic disease that circulates mainly among animals that are small and also their fleas. The disease can also occur in humans. Transmission between small animals and human beings occurs due to bite of fleas that are infected, inhalation, direct contact and ingestion of materials that are infected. In humans, plague is a dangerous disease with high mortality rates. Infact, in those who are untreated, the case-fatality rate is 30-60 percent (WHO, 2011). There are basically 3 forms of plague, namely, bubonic plague, septicemic plague and pneumonic plague. Of these the most common form in bubonic plague (WHO, 2011) and this will be discussed in this essay. Pathogenesis Yersinia pestis is an anerobic facultative gram-negative intracellular bacillus (Dufel, 2009). The organism is mainly transmitted from host to human beings through bite of a vector. The host is usually rodent and vector is flea. Other sources of transmission are close contact with body fluids or tissues contaminated or infected with the organism and inhalation of aerosolized bacteria. There are more than 200 different rodents and these serve as hosts. the vector flea is Xenopsylla cheopis (Dufel, 2009). So far, about 30 different species of flea have been identified (Dufel, 2009). Other carriers of plague causing bacillus include human lice and ticks. there are certain rodents that are resistant to infection like deer mice and wood rates. These however form an enzootic stage in which the bacillus survives long-term. Sometimes, the fleas transfer the pathogenic bacteria to animals that are susceptible to the disease like ground squirrels. Whenever large number of host animals die, the hungry fleas search new sources of food. This is the epizootic stage and this stage helps spread of organisms to newer territory. When human beings are infected from wild animals, a sylvtic stage occurs. Most carnivores are resistant to the disease, but they can act as transfer vectors. Birds, reptiles, hoofed animals and fish are resistant to the disease (Dufel, 2009). Virulent plague-causing organism survive in soil, grains, animal carcasses, flea feces, dried sputum and buried bodies (Ayyadurai et al, 2008). 80- 85 percent cases are bubonic form (Dufel, 2009). Bubonic plague is caused by deposition of the bacillus in the skin because of the bite of flea. The bacillus proliferates in the esophagus of the flea, preventing the entry of food into the stomach, This causes starvation and to overcome this, the flea starts sucking blood. In the process of swallowing, recoiling of the distended bacillus-packed esophagus occurs, thus depositing bacillus into the skin of the victim. The bacillus then invades the lymphoid tissue near the site of bite, producing bubos which are nothing but lymph nodes that have become necrotic, inflamed and hemorrhagic due to pathophysiology of the disease. Untreated bubonic plague can eventually lead to bacteremia and septicaemia. The bacillus has the capacity to seed every organ, including the liver, lungs, spleen, kidneys and even the meninges. The most virulent form of plague is the pneumonic plague. This occurs when the bacilli get deposited in the vasculature. In this condition, there occurs early dissemination and no bubo formation is seen. Such a pathology is seen when the bite occurs in regions of high vascularity like tonsils, pharynx and oral mucosa (Dufel, 2009). Epidemiology The disease is endemic in several countries in the world like Africa, Asia, the Americas and the former Soviet Union. According to WHO (2011), " in 2003, 9 countries reported 2118 cases and 182 deaths. 98.7% of those cases and 98.9% of those deaths were reported from Africa." The distribution of plague endemicity depends on the geographical distribution of the natural foci of infection, the small animals and fleas (WHO, 2011). Bubonic plague has occurred as several epidemics in the world. The first recorded epidemic was during the 6th century in the Byzantine empire. The most devastating epidemic of the disease, known as Black death occurred in Europe in the 14th century (Barenblatt, 2004). It has been thought the the origin of this epidemic was in Gobi desert. It spread to other parts through trade route. Other infamous epidemics include the Great Plague of Seville in the year 1649, the Great Plague of London between1665–1666, the Great Plague of Vienna in 1679, and the Great Plague of Marseille in 1720 (Barenblatt, 2004). It has been thought that the famous nursery rhyme, "Ring Around the Rosy" was derived from the symptom and course description of the disease. The most recent epidemic of plague, actually the third pandemic began in the mid-19th century in Central Asia (Barenblatt, 2004). Plague was used a biological warfare in the second Sino-Japanese war and also during Khabarovsk War Crime Trials (Barenblatt, 2004). Epidemiological factors that increase the risk of development of plague are non-urban residency, contact with sick animals, fleabite, veterinarian occupation and summer months (Dufel, 2009). Prognosis Mortality associated with bubonic plague is 1-15 percent. In untreated cases, the mortality is 40- 60 percent. The mortality of septicemic plague is 40 percent and in untreated cases, it is 100 percent. Pneumonic plague has 100 percent mortality if untreated in the first 24 hours. More than 50 percent cases occur in those less than 20 years of age (Dufel, 2009). Clinical presentation The incubation period is 1-6 days depending on the vulnerability of the host and the virulence of the organism (Dufel, 2009). Once the symptoms begin, the progress is rapid. A typical history of travel to the regions infested with fleas may be present. Some of the symptoms include fever with chills, myalgia, sore throat, headache, weakness, malaise, lymph nodes that are painful, enlarged and painful. Other symptoms include abdominal pain, nausea, vomiting, hematemesis, diarrhoea, constipation, cough, shortness of breath and stiff neck. Physical examination findings include high temperature, tachypnea, tachycardia and hypotension. The most commonly involved lymph nodes in bubonic plague are inguinal. In more than 60 percent of the cases inguinal bubos are seen. other lymph nodes that may be involved include cervical lymph nodes, epitrochlear lymph nodes and axillary lymph nodes. In children cervical or submandibular bubos are more common (Dufel, 2009). Many a times, maculopapular lesions may be found at the site of fleabite. Other dermatological findings include ecchymosis, acral cyanosis, petechiae and digital gangrene. These dematologic findings have given the name "Black death" to plague. On auscultation, diffuse crepitations may be heard in the lungs. Some areas may be dull to percuss. Abdominal tenderness may occur with or without guarding. There may be splenomegaly and hematochezia. Nuchal rigidity and diffuse joint and muscle tenderness can occur. the patient may have altered sensorium. In meningeal involvement, seizures can occur. The patient can bleed from any cavity or site. peripheral thrombosis secondary to disseminated intravascular coagulation can lead to peripheral thrombosis, gangrene and necrosis (Dufel, 2009 ). Differential diagnoses of plague are cat scratch disease, gas gangrene, necrotizing fascitis, disseminated intravascular coagulation, scarlet fever, tick-borne disease and rocky mountain spotted disease. Laboratory studies Complete blood picture will reveal raised leucocytes to more than 20,000 cell per cmm. Usually, there is shift to left. In septic shock however, the count may be low. Urinalysis may demonstrate red cell casts, hematuria and proteinuria rapid urine dipstick tests are present to screen for Yersinia pestis antigen and this can be used for rapid identification n field. Arterial blood gas analysis may reveal acidosis with or without hypoxia. In more than 20 percent patients, Yersinia pestis coccobacillus can be identified in peripheral smear. On gram staining, gram-negative coccobacillus that is pleomorphic can be identified. The gram stain test can be performed on sputum, blood and bubo aspirate. On Giemsa or Wright staining, bipolar safety pin structure can be seen. Plague bacilli can be cultured easily on most culture media. However, since the growth is slow, more than 48 hours is essential prior to identification of colonies. Blood culture is positive in more than 85 percent cases. Even buboaspirate culture is positive in more than 80 percent cass. Sputum culture is positive only when lungs are involved (Dufel, 2009). Imaging studies do not have much role in the diagnosis of bubonic plague. Infiltration of the alveoli with or without lymphadenopathy is suggestive of pneumonic plague. Bilateral consolidation may be seen (Dufel, 2009). In some laboratories and at the CDC, specialized diagnostic testing may be seen. Currently new F-1 rapid test using monoclonal antibodies has come up. Fluorescent antibody staining of the organisms can be done on sputum, blood and buboaspirates. Even antibody titers are available. Acute hemagglutination and convalescent passive hemagglutination titers must be taken 10 days apart. A 4-fold difference or a single convalescent PHA titer of 1:16 is evidence of infection (Dufel, 2009). Needle aspiration may need to be done to send the aspirate for testing: gram stain and culture. Aspirate may be attempted even when the node is hard and fluctuant. Instillation of about 1-3 ml of normal saline prior to aspiration yields more aspirate for testing. The person who is performing the procedure must take severe measures with regard to contact and respiratory precautions (Dufel, 2009). Treatment Rapid diagnosis and immediate treatment is essential to prevent complications and fatality related to plague (Prentice et al, 2007). If diagnosis is established on time and appropriate treatment is instituted immediately, patients can be cured of the disease. Treatment of bubonic plague mainly involves supportive care and antibiotics. Infusion of crystalloids must be done to hydrate the patient well and keep the vital signs within normal limits. oxygen must be administered either through nasal cannula or mask based on the respiratory distress situation of the patient. Pulse oximetry must be used to determine respiratory compromise. health professionals dealing with patients suffering from plague must take universal precautions like gloves, goggles, masks and gown to prevent contraction of the infection. Monitoring of urine output is critical in the management of plague. In case of septic shock, invasive hemodynamic monitoring must be done and crystalloids and vasopressor agents must be given as needed. In respiratory compromise, intubation and mechanical ventilation must be done with positive end-expiratory pressure. Colloids, antipyretics and antiulcer agents may be used as required (Prentice et al, 2007). The patient must be isolated and treated. In case respiratory symptoms are present, strict isolation with universal precautions must be taken during the first 96 hours of admission and treatment. Only 48 hours of isolation is necessary in only bubonic plague. All the contaminated material must be autoclaved or incinerated. The laboratory personnel must be informed about sample infected with plague (Dufel, 2009). The patients must be treated with antibiotics. Antibiotics to which Yersinia pestis is sensitive are gentamycin, streptomycin, chloramphenicol, doxycycline, ciprofloxacin, tetracycline and co-trimoxazole. Gentamycin is the drug of choice. The dose in adults is 5mg/kg every 6 hours. In children, the dose is 2.5 mg/kg every 8 hours. the dosage must be adjusted as per renal status. This drug is used in combination with a secondary agent. The next drug of choice is streptomycin. The treatment is given only for 5 days because of its toxic side effects. It must be given with a secondary agent that must be continued for 10 days. The dose in adults is 30mg per kg per day in 2-4 divided doses. In children, the dose is 20-30mg/kg in 3-4 divided doses. Chloramphenicol is recommended as a secondary agent, especially in meningitis due to plague, because of its high penetration into CNS. It is also recommended in profound hypotension and also when pleurae or pericardium are involved. It is the drug of choice in pregnant women. The dosage in adults is 50-100 mg per kg per day in four divided doses. In children, the dose is 25-50mg per kg per day in 2-4 divided doses. Doxycycline is useful as a secondary agent in the treatment of plague. It is also useful for postexposure prophylaxis. The loading dose in adults is 200 mg, following which 100mg is given twice a day for 10 days. In children, the dose is 2.2mg per kg twice a day. Ciprofloxacin is useful as a secondary agent. It is also useful for post-exposure prophylaxis. The dose in adults is 400mg IV or 500mg oral twice a day. In children, the dose is 15mg per kg in two divided doses. other secondary agents include tetracyclines and cotrimoxazole (Dufel, 2009). Prevention Education is the main strategy to prevent plague In areas where zoonotic plague is active people must be informed and educated about measures to be taken to prevent flea bites. Preventive measures also include careful disposal of animal carcasses. People must be advised to avoid direct contact with infective tissues and also from being exposed to those suffering frm pneumonic plague (WHO, 2011). Case recognition and field investigation Whenever a case of plague has been reported, the most likely source of infection must be identified. This is possible by looking at the area from which the human case was reported and typically "looking for clustered areas with large numbers of small animal die-offs" (WHO, 2011). Exposure source can be stopped by proper control, hygiene, precautionary and sanitary measures. Information about the disease must be provided to public, health authorities and health professionals in that area so that preventive measures and early identification of the disease is made. Verification with regard to appropriate initiation of right antibiotics must be made and stock supply of some more antibiotics must be made available in case of appearance of the disease in some more people. Patients with pneumonic plague must be strictly identified. Specimens for laboratory confirmation must be obtained, sent and followed up (WHO, 2011). Vaccination Plague vaccines were available a couple of decades ago. But they were not effective and hence their use is not recommended now. In immediate outbreak situations also these vaccines are not recommended. Currently, vaccination is recommended only in high risk people like laboratory personnel. Surveillance and control WHO (2011) suggests that surveillance officers must conduct investigations to identify small animals and species of flea that are implicated in the zoonotic cycle of flea in the concerned region and take measures to develop a programme, especially on the environmental management with intentions to limit the spread of the disease. Surveillance officers must also take active long terms measures to identify zoonotic foci of the disease and take rapid response whenever such foci are identified so that in epizootic outbreaks, human plague cases are reduced (WHO, 2011). References Ayyadurai, S., Houhamdi, L., Lepidi, H., Nappez, C., Raoult, D., Drancourt, M. (2008). Long-term persistence of virulent Yersinia pestis in soil. Microbiology, 154, 2865-71. Barenblatt, D. (2004). A Plague upon Humanity, 220–221. Dufel, S.E. (2009). CBRNE - Plague. Emedicine from WebMD. Rretrieved on 20th Feb, 2011 from http://emedicine.medscape.com/article/829233-overview Prentice, M. B. (2007). Plague. Lancet, 369(9568), 1196-207. WHO. (2011). Plague. Media Center. Retrieved on 20th Feb, 2011 from http://www.who.int/mediacentre/factsheets/fs267/en/ Read More