Marburg Haemorrhagic Fever: A Review

Shashikant Pattan1, Nachiket Dighe*1, Sanjay Bhawar2, Vinayak Gaware1, Deepak Musmade1, Mangesh Hole1, Smita Parjane1, Mayur Bhosale1 and Sapana Nagare1

¹Department Of Medicinal Chemistry,Pravara Rural College Of Pharmacy,Pravaranagar, M.S, India

²Dept of Pharmacology, Pravara Rural College of Pharmacy, Pravaranagar, Loni 413713, India

ABSTRACT

Marburg virus belongs to the same virus family, filoviridae, as the virus, which causes Ebola haemorrhagic fever. Marburg virus was first recognized in 1967 when outbreaks of haemorrhagic fever occurred in Marburg and Frankfurt in Germany and in Belgrade in the former Yugoslavia. Multiple organ failure Severe bleeding, Jaundice ,Delirium ,Seizures ,Coma and Shock are common symptoms. Nosocomial transmission via contaminated syringes and needles has been a major problem. Transmission by droplets and small-particle aerosols was observed in outbreaks among experimentally infected (Marburg) and quarantined imported monkeys. Many people were infected as a result of being exposed to African green monkeys imported from Uganda. Secondary spread of the disease is via contact with infected persons or contact with blood, secretions, or excretions of infected persons.  The virus may continue to be shed in the patient's semen for up to 3-4 months after illness. One reason the viruses are so deadly is that they interfere with the immune system's ability to mount a defense. ELISA can reveal the correct diagnosis.Till today, no vaccine is available but supportive hospital therapy should be utilized including balancing the patient’s fluids and electrolytes, maintaining their oxygen status and blood pressure, replacing lost blood and clotting factors and treating them for any complicating infections.

Keywords: Marburg virus, haemorrhagic fever, Filoviruses

Introduction:

The viral structure is typical of filoviruses, with long thread like particles, which have a consistent diameter but vary greatly in length from an average of 800 nanometers up to 14,000 nm, with peak infectious activity at about 790 nm. Virions (viral particles) contain seven known structural proteins. While nearly identical to Ebola virus in structure, Marburg virus is antigenically distinct from Ebola virus in other words; it triggers different antibodies in infected organisms. It was the first filovirus to be identified. Marburg virus was briefly described in the book written by Richard Preston entitled The Hot Zone. Genera Marburg virus Ebola virus Filoviruses are viruses belonging to the family Filoviridae, which is in the order Mononegavirales.¹

Epidemiology:

The reservoir of filoviruses remains a mystery. Species such as guinea pigs, primates, bats and hard ticks have been discussed as possible natural hosts; however, no non-human vertebrate hosts or arthropod vectors have been identified. Person-to-person transmission by intimate contact is the main route of infection in human outbreaks ⁵. Transmission seems to be inefficient, as documented by secondary attack rates rarely exceeding 10%. Nosocomial transmission via contaminated syringes and needles has been a major problem, especially in the 1976 and 1995 Ebola outbreaks in Zaire. Transmission by droplets and small-particle aerosols was observed in outbreaks among experimentally infected (Marburg) and quarantined imported monkeys (Ebola Reston, 1989-90).

History of Infection:

Table 1: History of Marburgs haemorrhagic fever

Year	Description
1967	25 people contracted Marburg haemorrhagic fever after handing material from infected monkeys, which were imported from Uganda.  An additional 6 people contracted the disease from the infected humans.
1975	An Australian contracted the disease while traveling through Zimbabwe and subsequently died after 12 days of illness. Two people who cared for him, his traveling companion and a nurse, contracted severe cases of the disease.  His companion contracted Marburg 7 days after the onset of his symptoms; the nurse contracted the disease 7 days after contact with the second patient.  Both companion and nurse survived.^2
1980	A French engineer contracted Marburg (and died); the physician who attempted to resuscitate the engineer contracted the disease, but survived
1982	A single occurrence; no secondary cases occurred.^2
1987	A young Danish man who, while traveling in western Kenya, had visited the same park as the French engineer.  No secondary cases occurred.
1988-2000	Most cases occurred in young male workers at a gold mine in Durba, in the northeastern part of the country, which proved to be the epicentre of the outbreak. Cases were subsequently detected in the neighboring village of Watsa.
2004-2005	Outbreak believed to have begun in Uige Province in October 2004. Most cases detected in other provinces have been linked directly to the outbreak in Uige ^3
2007	Small outbreak, with 2 cases, one fatal, in young males working in a mine. To date, there have been no reported cases among health workers
2008	A 40-year-old Dutch woman with a recent history of travel to Uganda was admitted to hospital in the Netherlands. Three days prior to hospitalization, the first symptoms (fever, chills) occurred, followed by rapid clinical deterioration. The woman died on the 10th day of the illness. ^3,4

This is supported by identification of filovirus particles in alveoli of naturally and experimentally infected monkeys. Courses of human outbreaks, however, indicate that aerosols and droplets do not seem important modes of transmission. Marburg and subtypes Sudan and Zaire of Ebola appear to be indigenous to the African continent and both Ebola subtypes have been isolated from human patients only in Africa ⁶. Marburg has been isolated from human patients in Africa and Europe; however, a virus, which originated in Africa, caused the European cases. The Ebola Reston outbreak Documented for the first time the presence of a filovirus in Asia. Serological studies (IFA) among captive macaques in the Philippines indicated that the source of Ebola Reston might be wild non-human primates. However, IFA-detected antibodies seem to be spurious and latent infection in non-human primates has never been observed Serological studies suggest filoviruses are endemic in many countries of the central African region. Recent serosurveys imply that filoviruses might also be endemic in other countries (Germany, United States, Philippines). Although serological data based on IFA are only of limited reliability, they at least suggest the possible occurrence of sub clinical infections caused by known or unknown filoviruses ⁷.

Life cycle

Two-host ixodid ticks have a life cycle that usually spans over two years.  Gravid females drop off the second host after feeding to lay eggs, usually in the fall ⁸.  Eggs hatch into six-legged larvae and overwinter in this stage.  The following spring, the larvae seek out and attach to the first host, usually a rodent or lagomorph.  The larvae molt into nymphs on the first host - .  Engorged nymphs drop off the first host, usually in the late summer or fall and overwinter in the nymphal stage.  Nymphs molt into adults the following spring and seek out the second host,

which is usually a larger herbivore (bovids, cervids, etc).  Adults feed on the second host during the summer and mate.  In the fall, females drop off the second host to continue the cycle ⁹.  Females may reattach and feed multiple times.  Humans may serve as first or second hosts for ticks with this life cycle.  Also, the second host does not necessarily have to be a separate species, or even a separate individual, as the first host ¹⁰.

Figure 1: Life Cycle of Haemorrhagic Fever

Occurrence

Marburg virus belongs to the same virus family, filoviridae, as the virus which causes Ebola haemorrhagic fever. Marburg virus was first recognized in 1967 when outbreaks of haemorrhagic fever occurred in Marburg and Frankfurt in Germany and in Belgrade in

Death and Cases of Marburgs haemorrhagic fever World Wide

Table 2: Marburgs haemorrhagic fever World Wide ¹⁴

Year	Location	Cases	Status	Dead	Mortality
1967	Germany and Yogoslavia	25 6	Primary secondary	7 0	28% 0%
1975	South Africa	1 2	Primary secondary	1 0	100% 0%
1980	Kenya	1 1	Primary secondary	1 0	100% 0%
1982	South Africa	1	Primary	1	100%
1987	Kenya	1	Primary	1	100%
1988-2000	Democratic Republic of Congo (DRC)	154	Primary	128	83%
2004-2005	Angola	252	Primary	227	90%
2007	Uganda	2	Primary	1	50%
2008	Netherlands ex Uganda	1	Primary	1	100%

the former Yugoslavia. Thirty seven people (seven fatalities) were infected as a result of being exposed to African green monkeys imported from Uganda. Outbreaks and sporadic cases have been reported in Angola, Democratic Republic of Congo, Kenya and South Africa ^{11, 12}.

Geographic Distribution of Marburg Haemorrhagic Fever Outbreaks and Fruit Bats of Pteropodidae Family

Figure 2: Distribution of Marburg Haemorrhagic Fever ¹³

a) Electron micrograph of Marburg virus: Ultra thin sections obtained from primary cultures of human endothelial cells three days post-infection. Particles consist of a nucleocapsid surrounded by a membrane in which spikes are inserted (arrows). The plasma membrane is often thickened at locations were budding occurs (arrowheads). Bar, 0.5 µm; bar inset, 50 nm.

b) Filoviral structural proteins. The ribonucleoprotein complex (RNP) consists of the nonsegmented negative-strand RNA genome and four of the structural proteins; nucleoprotein (NP); virion structural protein (VP) 30; VP35; L (large or polymerase) protein. VP24 and VP40 are membrane-associated proteins and the spikes are formed by the glycoprotein (GP) ¹⁵.

Vector

The natural reservoir for the virus is unknown.  Epidemiologists have tested bats, monkeys, spiders and ticks for the virus, but were not able to acquire definitive data.  Common factors indicate that the natural reservoir is part of rural Africa.  Secondary spread of the disease is via contact with infected persons or contact with blood, secretions, or excretions of infected persons.  The virus may continue to be shed in the patient's semen for up to 3-4 months after illness.  Sexual transmission of the disease did occur in one instance in Germany ¹⁶.

Distribution of Marburgs haemorrhagic fever in Africa

Figure 3: Marburgs haemorrhagic fever in Africa ¹⁴

Natural reservoir

In September 2007, New Scientist magazine reported that the virus has been found in cave-dwelling African fruit bats in Gabon, the first time the virus has been found outside primates. The virus has now also been confirmed in bats in a Uganda mine after two miners contracted Marburg in August 2007. Ebola antibodies (a close relative to Marburg) were found in three species of fruit bats in 2005. Marburg antibodies have been found in healthy bats, suggesting that the bats had been previously infected. Although no one has yet found complete live viruses from a bat, the team suggests that “think we can be sure that these fruit bats are the reservoir of Marburg virus”. The same techniques used to identify those genes were also used to identify Marburg genes found in Egyptian fruit bats, Rousettus aegyptiacus.¹⁷

Virus Structure

Figure 4: Structure of Marburg virus

Pathogenesis Mechanism

After gaining access to the body, filoviruses initially infect monocytes, macrophages and other cells of the mononuclear phagocytic system (MPS), probably in regional lymph nodes. Some infected MPS cells migrate to other tissues, while virions released into the lymph or bloodstream infect fixed and mobile macrophages in the liver, spleen and other tissues throughout the body. Virions released from these MPS cells proceed to infect neighboring cells, including hepatocytes, adrenal cortical cells and fibroblasts Infected MPS cells become activated and release large quantities of cytokines and chemokines, including TNF-, which increases the permeability of the endothelial lining of blood vessels. Endothelial cells apparently become infected by virus only in the later stages of disease ¹⁸. Circulating cytokines contribute to the development of disseminated intravascular coagulation (DIC) by inducing expression of endothelial cell-surface adhesion and procoagulant molecules and tissue destruction results in the exposure of collagen in the lining of blood vessels and the release of tissue factor Massive lysis of lymphocytes occurs in the spleen, thymus and lymph nodes in the late stages of filovirus infection ¹⁹. There is no sign that the lymphocytes themselves are infected, rather they die through apoptosis, perhaps induced by cell-surface binding of chemical mediators released by MPS cells or by a viral protein. Secondary spread of the disease is via contact with infected persons or contact with blood, secretions, or excretions of infected persons.  The virus may continue to be shed in the patient's semen for up to 3-4 months after illness.  ²⁰

Signs and Symptoms

Marburg haemorrhagic fevers lead to death for a high percentage of people who are affected. As the illness progresses, it can cause:

· Multiple organ failure

· Severe bleeding

· Jaundice

· Delirium

· Seizures

· Coma

· Shock ^23,24

Death often occurs less than 10 days from the start of signs and symptoms ²³. One reason the viruses are so deadly is that they interfere with the immune system's ability to mount a defense. But scientists don't understand why some people recover from Ebola and Marburg and others don't. For people who survive, recovery is slow. It may take months to regain weight and strength and the viruses remain in the body for many weeks.

People may experience:

· Hair loss

· Sensory changes

· Liver inflammation (hepatitis)

· Weakness

· Fatigue

· Headaches

· Eye inflammation

· Testicular inflammation ^{25, 26}

Figure 5: Mechanism of Marburg virus

Mode of infection

Figure 6: Mode of Infection ^{21, 22}

Fatality Rate

The case-fatality rate for Marburg haemorrhagic fever is between 23-25%.²⁷

Incubation Period

After an incubation period of usually 4-10 days there is an abrupt appearance of illness with initially nonspecific symptoms, including fever, severe headache, malaise, myalgia, bradycardia and conjunctivitis. ^{28, 29}

Complications after recovery

Recovery from Marburg haemorrhagic fever may be prolonged and accompanied by orchititis, recurrent hepatitis, transverse myelitis or uvetis. Other possible complications include inflammation of the testis, spinal cord, eye, parotid gland, or by prolonged hepatitis.^{30, 31}

Diagnostic Tests

1. Organism Detection Tests

· Electron Microscopy

· Transmission electron microscopy

· Immunofluroscence

· Virus isolation in animals ³²

2. Immunoassay Tests

· Hemagglutination

· Competitive and Two-Antibody ELISA

· IgM-capture antibody ELISA

· ELISA

· Indirect Fluorescent Antibody (IFA)

· Enzyme immunoassay ³³

3. Nucleic Acid Detection Tests

· One tube RT-PCR

· Real-time reverse transcription-PCR ³⁴

Figure 7: Signs and Symptoms

Transmission Information

1. From: Homo sapiens To: Homo sapiens , With Destination: Homo sapiens
Mechanism: Just how the animal host first transmits Marburg virus to humans is unknown. However, as with some other viruses, which cause viral haemorrhagic fever, humans who become ill with Marburg, haemorrhagic fever may spread the virus to other people. This may happen in several ways. Persons, who have handled infected monkeys and have come in direct contact with their fluids or cell cultures, have become infected. Spread of the virus between humans has occurred in a setting of close contact, often in a hospital. Droplets of body fluids, or direct contact with persons, equipment, or other objects contaminated with infectious blood or tissues are all highly suspect as sources of disease ³⁴

2. From: Primates To: Homo sapiens , With Destination: Homo sapiens
Mechanism: Persons who have handled infected monkeys and have come in direct contact with their fluids or cell cultures, have become infected ³⁵

Risk for the illness

People who have close contact with a human or nonhuman primate infected with the virus are at risk. Such persons include laboratory or quarantine facility workers who handle non-human primates that have been associated with the disease. In addition, hospital staff and family members who care for patients with the disease are at risk if they do not use proper barrier nursing techniques.³⁵

Prevention

Barrier nursing techniques: Due to our limited knowledge of the disease, preventive measures against transmission from the original animal host have not yet been established. Measures for prevention of secondary transmission are similar to those used for other haemorrhagic fevers. If a patient is either suspected or confirmed to have Marburg haemorrhagic fever, barrier-nursing techniques should be used to prevent direct physical contact with the patient. These precautions include wearing of protective gowns, gloves and masks; placing the infected individual in strict isolation; and sterilization or proper disposal of needles, equipment and patient excretions. ³⁶

Treatment

A specific treatment for this disease is unknown. However, supportive hospital therapy should be utilized. This includes balancing the patient’s fluids and electrolytes, maintaining their oxygen status and blood pressure, replacing lost blood and clotting factors and treating them for any complicating infections.Sometimes treatment also has used transfusion of fresh-frozen plasma and other preparations to replace the blood proteins important in clotting. One controversial treatment is the use of heparin (which blocks clotting) to prevent the consumption of clotting factors. Some researchers believe the consumption of clotting factors is part of the disease process.³⁷

Vaccine

None as with exposure to other filoviruses, exposure to Marburg does not confer subsequent immunity. The antibody response in convalescent patients does not neutralize or protect against subsequent infection by Marburg virus.³⁷

Prognosis

The case-fatality rate for Marburg haemorrhagic fever is between 23-25%. Recovery from Marburg haemorrhagic fever may be prolonged and accompanied by orchititis, recurrent hepatitis, transverse myelitis or uvetis. Other possible complications include inflammation of the testis, spinal cord, eye, parotid gland, and prolonged hepatitis.³⁸

Weaponization

The former Soviet Union reportedly had a large biological weapons program involving Marburg. The development was conducted in Vector Institute under the leadership of Dr. Nikolai Ustinov, who died after accidentally injecting himself with the virus. The post-mortem samples of Marburg taken from Dr. Ustinov's organs were more powerful than the original strain this new strain, called "Variant U," was successfully weaponized and approved by Soviet Ministry of Defense in 1990. Bioterrorism grants in the United States are funding research to develop a vaccine for Marburg virus. ^{38, 39}

CONCLUSION:

Marburg virus, one of the causes of haemorrhagic fever, creates serious complications like inflammation of the testis, spinal cord, eye, parotid gland, and prolonged hepatitis. The antibody response in convalescent patients does not neutralize or protect against subsequent infection by Marburg virus. Therefore vaccine is not available. Only supportive hospital therapy should be utilized with symptomatic treatment. Sometimes treatment may need transfusion of fresh-frozen plasma and other preparations to replace the blood proteins important in clotting. However early diagnosis will help in controlling disease severity.

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Received on 25.09.2009

Accepted on 30.09.2009

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Research J. Pharmacology and Pharmacodynamics 2009; 1(2): 50-55