exotic viral infections and the liver

Introduction

• Exotic: “originating in a foreign country”, here referred to infections acquired in the tropics.

• The increase in international travel and the speed of transportation exported to countries where they are not endemic.

• Physicians should learn to recognize unusual infections and to face the possible public health consequences of the introduction of these infections in their countries.

Liver involvement in infections by exotic viruses

• The liver is often affected: – Primary target organ– Only marginally affected– In very few cases the infection is only

hepatotropic.

Exotic viruses and the liver

• Dengue fever • Yellow fever• Rift Valley fever• Crimean/Congo haemorrhagic fever• Lassa fever• Marburg and Ebola virus diseases• Others

DENGUE

Epidemiology of Dengue Fever

• Annual incidence:• 100 million cases of Dengue

fever

• 250.000 cases of Dengue haemorrhagic fever

• mortality rate of 24,000-25.000 (W vs developing countries)

The most prevalent mosquito-borne viral disease. Transmitted by mosquito bite (usually Aedes aegypti, but trasmission by Aedes albopictus and Aedes polynesiensis also described).

CDC 2009

Breeding Grounds for Mosquitoes

Epidemiology of Dengue Fever

• 10.4 % of post-travel systemic febrile illnesses (second to malaria).

Freedman. N Engl J Med 2006

Population growth, urbanization and air travel closely tied with resurgence of epidemic DF and emergence of DHF in the 20th century.

Dengue virus

• RNA virus. Flaviviridae family.

• Four serotypes (DENV 1-4).– People living in an area of endemic dengue

can be infected with three or four dengue serotypes during their lifetime.

– Types 2 and 4 more likely to cause inapparent infections

Clinical presentation of Dengue Fever

• Asymptomatic infection

• Self-limited dengue fever

• Dengue haemorrhagic fever with shock syndrome

Risk of severe disease is much

higher in sequential rather

than primary dengue infection

Incubation period : 3-14 days it can be excluded in a traveler developing an illness more than 14 days after returning from a dengue-

endemic country.

Clinical presentation of Dengue Fever

Classic dengue fever (DF):

– Acute febrile illness rash, headache and marked muscle and joint pains.

– Haemorrhagic manifestations are common but in rare cases can be life-threatening.

Dengue Shock syndrome (DSS)

Dengue haemorrhagic fever (DHF):

Increased vascular permeability (the most specific and life-threatening feature of DHF)

Marked thrombocytopaenia (<100,000 cells/mm3)

Fever

Haemorrhagic tendency

+/- shock

World Health Organization

“break-bone fever”

Controversy regarding classification system of Dengue Fever

• Dengue – Without warning signs.– With “warning signs”: abdominal pain persistent vomiting,

clinical fluid accumulation, mucosal bleeding, lethargy, liver enlargement >2 cm or increase in hematocrit and rapid decrease in platelet count.

• Severe dengue: – severe plasma leakage, – severe haemorrhage or – severe organ impairment (defined as AST or ALT >1000,

impaired consciousness, or severe involvement of the heart or other organs).

World Health Organization. Geneva 2009

Currently, WHO have adopted a new and easier revised classification:

Liver involvement in Dengue Fever

• The liver is not the main target organ hepatic disease has been considered as unusual manifestation.

• However, clinical and experimental observations suggest that liver involvement occurs during dengue infections.

Evidence of liver involvement in Dengue Fever

% abnormal AST

% abnormal ALT

% normal AST

% slightly elevated ALT

% significantly elevated ALT

Series1

% abnormal AST

% abnormal ALT

ALT/AST>10 times

Kuo (1992) Souza (2004)

Mohan (2000)Nimmannitya (1987)

270 pt 1585 pt

145 pt 37 children


Elevation AST is greater than ALT

Nguyen (1997)

Parkash (2010) Kuo (1992)

Souza (2004)45 pt 1585 pt

699 pt 270 pt

% abnormal AST

% abnormal ALT


Elevation AST is greater than ALT

Differs from viral hepatitis: useful for differential diagnosis.

The exact significance of this pattern is uncertain. It has been suggested that may be due to excess release of AST

form damaged myocytes (Chung 1992).


• Aminotransferases peak 9th day after first symptoms and go back to normal within 3 weeks.

• Liver failure has been documented after resuscitation from shock, and, in some cases, may be caused by prolonged hypotension rather than a direct viral effect hypoxic hepatitis


• Dengue viral antigens within hepatocytes,virus appears to replicate in both hepatocytes and Kupffer cells (Huerre 2001).

• Liver cellular apoptosis in vivo and in vitro (Couvelard 1999; Marianneau 1996, 1997).

• Mid-zone and centrilobular necrosis, fatty alterations, hyperplasia of the Kupffer cells, acidophil bodies and monocyte infiltrations of the portal tract with DHF.


Mild and moderate hepatitis are more frequent than severe hepatitis

However, severe hepatitis appear to be higher in DHF/DSS

Parkash (2010) Souza (2004)


Mild and moderate hepatitis are more frequent than severe hepatitis

However, severe hepatitis appear to be higher in DHF/DSS

DF

DHF

Elevation AST/ALT

DF

DHF

Mean levels ALT

P>0.05

Wahid (2000)


• Fulminant hepatic failure complicating severe DHF/DSS has also been documented, and is associated with a poor prognosis.

Alvarez and Ramirez-Ronda 1985

Lawn 2003

Munasinghe and Rajasuriya 1967

Nguyen 1997

Subramanian 2005


Severe liver dysfunction associated with worst prognosis

Parkash (2010)699 patients

Also higher rate of:• bleeding• renal failure• acalculous cholecystitis

Dengue shock syndrome in a liver transplant recipient

– 3 weeks after transplant and died 2 days after admission with DSS.

– Serum quantitative PCR and liver tissue immunohistochemistry and PCR confirmed the dengue diagnosis of type 3 dengue virus.

– No documented previous history of dengue infection

Garcia. Transplantation. 2006

Diagnosis of Dengue Fever

• Based mainly on clinical signs and symptoms in endemic countries.

• Viral isolation and/or serotyping useful for future risk of DHF in individuals exposed to different serotypes.

• MAC-ELISA: IgM antibodies– Rapid diagnosis

– Sensitivity and specificity much lower than the HI assay

– In countries with serologic assays available, is the procedure of choice. If negative and the clinical suspicion is high, testing paired acute and covalescent serum by HI or ELISA.

Rothman. Uptodate 2010

Treatment and prevention of Dengue Fever

• Supportive

• There is no vaccine available.

YELLOW FEVER

Epidemiology of Yellow Fever

• First recognized in the 17th Century in Central America.• The disease occurs in tropical regions of South America and sub-

Saharan Africa.• Heterologous Flaviviral (previous Dengue) immunity thought to

provide partial protection and low incidence of YF in Asia.

OMS 1985-99

OMS: 200,000 cases of clinical disease (90% in Africa) and 30,000 deaths per each year (possibly underestimated).

Epidemiology of Yellow Fever

• Flavivirus transmitted by Aedes aegypti (human-to-human transmission in the absence of the mosquito does not occur).

• Three transmission cycles:

Liver involvement in Yellow Fever

• The liver is the main target organ, but other tissues (especially kidneys) become infected.

• Kupffer cells are initially infected

• Hepatocytes subsequently infected directly via Kupffer cells or haematogenously.

• Eosinophilic degeneration with Councilman bodies (apoptosis), rather than by ballooning and necrosis seen in A-E hepatitis.


• In fatal cases, amorphous masses (Torres bodies) or small, granular, yellow bodies (Villela bodies) can also be seen. Not diagnostic.

• Liver cells death is due to apoptosis (Councilman bodies).– Hepatocytes in the midzone of the lobe express Fas

ligand and lymphocytes infiltrated the liver mediate apoptosis.

Quaresma. Virology 2006

• There is no disruption of the reticular architecture of the liver, even in fatal cases.

Clinical features in Yellow Fever

• Incubation period: 3-6 days

• Classical illness 3 stages:– Period of infection– Period of remission– Period of intoxication


– Period of infection

• Pulse rate is slow relative to the height of the fever Faget´s sign

• Transaminases start to rise which precede the appearance of jaundice.

Tongue is characteristically red at the tips and sides, with white coating in the center.

Fever and non specific generalized malaise, headache, pain in lower extremities, myalgia, anorexia, vomiting, irritability and dizzness.


– Period of remission• Lasting up 48 h may follow the period of infection,

characterized by abatement of fever and symptoms.

• Patients with abortive infections recover at this stage.

• 15% enter the third stage.


– Period of intoxication• On the 3th to 6th day after the onset of infection

• Return fever, prostration, nausea, vomiting, epigastric pain, jaundice, oliguria, albuminuria and a haemorrhagic diathesis (GI bleeding, hematuria, metrorrhagia, petechiae...).

• Viremia teminates and neutralising antibodies appear in the blood.

• Characterized by variable dysfunction of multiple organs: LIVER, kidneys and cardiovascular system.

• 20-30% of the patients who enter this period die.


• AST levels > ALT, probably due to viral injury to the myocardium and skeletal muscle.– Useful to distinguish from other viral hepatitis.

• Levels are proportional to disease severity and might remain elevated for up to 2 months after onset.

Oudart. Bull World Health Organ 1979

• Advanced disease encephalopathy

• Global reductions in clotting factors synthesized by the liver contribute to bleeding. DIC may also be involved.

Yellow fever vs Lábrea Hepatitis

• The Brazilian Amazon Basin: – highly endemic area: YF,HBV and delta viral hepatitis. – an unusual type of fulminant hepatic failure Lábrea

hepatitis (LH).

• LH courses with hepatic failure and death . Associated with HBV and delta virus.

Fulminant YF and LH cases may present a similar clinical course.

Liver Histology in fulminant hepatic failure in northern Brazil: YF and LH

• Extensive necrosis, portal and hepatic vein phlebitis and morula cells + defective pattern of hepatocellular regeneration and fibrous portal and acinar proliferationpossibly resulting from cumulative viral cytopathic from livers already affected by chronic hepatitis.

Extensive midzonal apoptosis, hepatocellular ballooning, protal phlebitis and remarkable regeration liver without previous lesion.

Evaluation 42 samples from fulminant hepatic failure in order to differentiate YF from LH.

LH YF

Dias Junior. 2006

Liver Histology in fulminant hepatic failure in northern Brazil: YF and LH

Dias Junior. 2006

Diagnosis of Yellow Fever

• Virus isolation– From the blood or post-mortem liver tissue

• Rapid diagnostic test:– Detection viral genome by PCR in blood o tissues– Not widely available

• Detection IgM antibodies (ELISA)– Simple sample provides a presumptive diagnosis. Confirmation is

made by a rise between paired acute and convalescent samples or a fall between early and late convalescent samples.

– Cross-reactions with other flaviviruses complicate the diagnosis particularity in Africa (multiple flaviviruses cocirculate).

Vaccine of Yellow Fever

• Liver attenuated virus

• Protective immunity occurs in 90% within 10 days and in nearly 100% within 3-4 weeks.

• Immunity probably is lifelong after a single dose, international certificate of immunizations is valid 10 years, a booster every 10 years.

• Adverse events : 43/100,000– >70 years 13.4 x

Department of Health and Human Services Centers for Disease Control and Prevention 2010

Travelers

• The risk for travelers is determined by multiple factors: vaccination status, location of travel, duration exposure…

• 1970-2009: nine cases of YF were reported in unvaccinated travelers from the United States and Europe in Africa or South America. Eight died.

• Only one case has been documented in vaccinated traveller.

RIFT VALLEY FEVER

Rift Valley Fever Epidemiology

• Zoonotic disease of domestic ruminants and humans, described in Kenya in 1931.

WHO 2009

Outbreaks have occurred in subSaharan Africa and Egypt (1976)

Rift Valley Fever and epidemiology

• Arbovirus belonging to genus Phlebovirus

(family Bunyaviridae).

• Transmitted by mosquito bites (Aedes mcintoshi as a main route), aerosol route or by close contact with the blood or organs of infected animals, especially during epizootics.

• No transmission person-to-person, but the blood of patients during the acute illness is highly infectious.

Liver and Rift Valley Fever

• The liver is the main target organ.– Invasion of the hepatocytes, causing midzonal

hyaline degeneration leading to necrosis and formation of Councilman bodies.

• Also, invasion of the endothelial cells vasculitis haemorrhagic phenomena.

Clinical manifestations for Rift Valley Fever

• Incubation period: 2-7 days.

• Most humans: non-specific, self-limiting febrile illness.

• <5% disease is much more severe 3 different clinical syndromes:– Extensive bleeding, hepatic failure, jaundice.– Encephalitis, confusion and coma.– Maculo-retinitis (~10%) damage may be permanent

Diagnosis in Rift Valley Fever

• Differential diagnosis is simple during epidemics and when the 3 typical clinical forms occur together in the same area (haemorrhagic, diathesis, encephalitis, and ocular disease).

• Confirmed by the PCR-RNA or detection of IgM antibodies by ELISA (exclusively in high-containment laboratories).

• Antibodies appear to 5-10 days after the onset.

Treatment

• No specific treatment for either humans or animals.

• Ribavirin may be effective in the treatment of RVF (even more in CCHF).

Prevention

• During epizootics the movement of animals from areas where the infection has been detected should be restricted.

• Two vaccines are avaliable for use in animals, a live-attenuated and inactivated vaccine.

• Experimental vaccines in humans.

• Insecticide treatments.

CRIMEAN/CONGO HAEMORRHAGIC FEVER

Introduction

• First description of human cases in 1940s in Crimea.

•

In 1956 a virus named Congo was isolated from a child in that country. In 1969 it was demonstrated that the two viruses were identical: Crimean/Congo haemorrhagic fever virus.

Severe hemorrhagic fever with a mortality rate ranging from 10-80% in different outbreaks.

Crimean/Congo virus and liver involvement

• Genus Nairovirus of the family Bunyaviridae.

• The infection is transmitted by ticks of the genus Hyalomma. Also, contact with the blood of an infected person during the acute phase of the disease.

• CHF resembles many other viral haemorrhagic fevers.

• Liver is often involved, with focal necrosis, often localized in the midzonal areas and with the presence of Councilman bodes.

Clinical manifestations of Crimean/Congo virus

• Incubation period: 3-7days

• Mild or asymptomatic infections may occur.

• Abrupt onset with fever, headache, nausea and vomiting.

• In some patients, after 4-5 days, severe hemorrhages develop with massive bleeding, hypotensive shock and death.

• There may be acute, icteric hepatitis.

Diagnosis of Crimean/Congo virus

• Antigen-capture by ELISA or RT-PCR

• Antibodies detection by ELISA.

• Isolation in cell cultures (high-containment laboratories).

Treatment and prevention of Crimean/Congo virus

• General supportive therapy is the mainstay

• A recent meta-analysis show that there is a very low quality evidence about Ribavirin being effective but no clear benefit from the current data.

• Although an inactivated vaccine has been developed and used on a small scale in Eastern Europe, there is no safe and effective vaccine widely available for human use.

Soares-Weiser 2010

MARBURG and EBOLA

Introduction

• Both are among the most virulent human pathogens, causing severe hemorrhagic fever that resembles fulminant septic shock.

• Fatality rates in epidemics in central Africa, including a large outbreak of Marburg hemorrhagic fever in Angola in 2005, have reached 80-90%.

• Bioterrorism: Category A

Epidemiology Marburg and Ebola Fever

• Since 1967, when the importation of infected monkeys from Uganda into Germany and Yugoslavia resulted in explosive outbreaks, all cases of filoviral hemorrhagic fever have occurred in sub-Saharan Africa.

Marburg and Ebola viruses

• RNA viruses. Family Filoviridae.

• Experimentally filoviruses can initiate infection via many routes, including ingestion, inhalation or passage through breaks in the skin.

Mahanty. Lancet Infect Dis 2004

• Aerosolized filoviruses are highly infectious for laboratory animals. However, epidemiologic studies have shown that these agents rarely spread from person to person by the respiratory route.

• No evidence that are carried by mosquitoes or other biting arthropods.

Epidemiology Marburg and Ebola Fever

• Study of these virus is extremely difficult, because outbreaks are

sporadic, far from optimal analyses and clearly contagious.•

The reservoirs host of the filoviruses is not known (nonhuman primates are at least as susceptible as humans to rapidly lethal filoviral HF).

• isolation of Marburg virus from fruit bats in Uganda showed cosiderable genetic diversity, suggesting that they had long been present in the bat population.

Towner. PLoS Pathog 2009

Pathogenesis Marburg and Ebola

• Systemic inflammatory syndrome by inducing proinflammatory mediators from infected macrophages and other cells.

• Coagulations defects (induced indirectly)– Infected macrophages Tissue Factor triggering the extrinsic

coagulation pathway.

• Impairment of adaptive immunity– Dendritic cells (primary responsibility for the initiation of adaptive

immune responses) major site of filoviral replication

– Lymphocytes remain uninfected, but undergo apoptosis induced by inflammatory mediators and/or the loss of support signals from dendritic cells. similar phenomenon is observed in septic shock.

Clinical manifestations Marburg and Ebola Fever

• Incubation period: 5-7 days

• Abrupt onset of fever, chills and general malaise and other non specifics sign and syntoms.

• Conjunctival haemorrhages, easy bruising. Gross bleeding is common only in moribund patients.

• Conjunctival injection and dark red discoloration of the soft palate

• Nonpruritic maculopapular rash on the upper body is a distinctive sign of filoviral infection.

Liver involvement Marburg and Ebola Fever

• Filoviruses cause multifocal hepatic necrosis.– Elevated serum AST > ALT

• In Marburg outbreak, transaminases rose rapidly on day 6 to 8 highest in patients who died.

– May also cause a decline in plasma levels of certain coagulation factors.

• Death usually occurs following a shock and hepatic failure.

Diagnosis Marburg and Ebola Fever

• Rapid diagnostic test: detection of viral antigens by ELISA or RT-PCR

• Culture: confirms the diagnosis.

Treatment Marburg and Ebola Fever

• No specific therapy is available.

• Replacement of blood, coagulation factors, and platelets, together with careful maintenance of hydration, are the mainstay of therapy.

• Ribavirin, which inhibits some other RNA viruses, is ineffective against these agents.

• Proof of concept trials have indicated that Ebola-targeted siRNAs may be effective as post-exposure prophylaxis in humans, with 100% of non-human primates surviving a lethal dose of Zaire Ebola virus, the most lethal strain.

LASSA FEVER

Epidemiology of Lassa Fever

• Zoonotic disease of rodents.

•

•

The first outbreak was in 1969 in Nigeria. Since then, is more prevalent and less frequently fatal than was supposed at first

Endemic in West Africa• 300,000 infections and 5000

deaths annually

CDC 2004

Epidemiology of Lassa Fever

• Family Arenaviridae.

• Mastomys natalensis, a common rat around human habitations in Africa, is the host.

• The virus spreads to humans primarily through direct contact with infected rats or by direct contact with water or food contaminated by rodent urine.

• Person-to-person transmission occurs.

Mastomys rodent, also known as the

"multimammate rat".

Liver involvement in Lassa Fever

• Lassa virus is pantropic, causing lesions and dysfunction in multiple organ systems.

• In experimentally infected animals, the highest concentration of virus is found in the liver.

• There is no correlation between the titre of virus in blood or liver tissue and the histological liver damage.

Liver involvement in Lassa Fever

• Four principal alterations:– Focal cytoplasmic degeneration of

hepatocytes

– Randomly distributed multifocal hepatocellular necrosis with Councilman bodies

– Monocytic reaction to confluent necrotic hepatoytes

– Hepatocellular mitoses

Clinical manifestations of Lassa Fever

• Incubation period: 7-18 days.

• 80% infections are asymptomatic.

• Similar clinical manifestations to other hemorrhagic fever viruses, with respiratory distress, hypovolemic shock, pulmonary oedema, and, sometimes, massive pleural effusions and ascites rapidly developing during the 2nd week in severe cases.

• The case fatality rate in pregnant women is much higher than in non-pregnant adults.

Laboratory findings of Lassa Fever

• Two reliable predictors of the outcome:

– AST>150UI/L – High viraemia

78% fatality rate (vs 17 % in patients who do not presents these features)

Johnson 1987

Diagnosis of Lassa Fever

– ELISA• Antigen detection is very useful in the early

diagnosis.• IgM antibodies.

– RT-PCR to detect virus this method is primarily a research tool.

Treatment of Lassa Fever

• Treatment of choice: Ribavirin– Can reduce mortality, especially when given

intravenously before day 7

– 2 g loading dose followed by 1 gr /6 h x 4 days; then 0.5 g/ 8 h x 6 days.

• Supportive care

Other viral haemorrhagic fevers occasionally affecting the liver

• Junin virus Argentina• Machupo virus Bolivia• Guanarito virus Venezuela

• Sabia Brazil• Chapare Bolivia• Flexal Brazil• Alkhurma Egypt

Arenavirus

Flavivirus

Signs and Symptoms of Dengue Fever

• High fever, up to 105 F (40.6 C)• A rash over most of your body, can subside after a couple of days

and then reappear• Sever headache, backache or both• Pain behind your eyes• Severe joint and muscle pain (breakbone fever)• Nausea and vomiting• Signs and symptoms usually begin about four to seven days after

being bitten by A. aegypti. • Mild dengue fever rarely causes death, it is usually self-limiting

Mayo clinic, (2010). Dengue fever symptoms. Retrieved April 19, 2010 from http://www.mayoclinic.com/health/dengue_fever/DS01028/DSECTION=symptoms

Signs and Symptoms of Dengue Hemorrhagic fever (DHF)

• A more severe form of dengue that begins the same way as dengue fever but become worse after several days

• Significant damage to your blood and lymph vessels• A decrease in the number of blood cells that help your

blood clot (platelets)• Bleeding from nose and mouth• Bleeding under the skin, which gives the appearance of

bruising• Death Mayo clinic, (2010). Dengue fever symptoms. Retrieved April 19, 2010 from

http://www.mayoclinic.com/health/dengue_fever/DS01028/DSECTION=symptoms

Signs and Symptoms of Dengue Shock Syndrome (DSS)

• The most severe form of the disease• It may start with the signs and symptoms of mild dengue

plus• Severe abdominal pain• Frequent vomiting• Disorientation• Fluid (plasma) leakage from blood vessels• Heavy bleeding• A sudden drop in blood pressure (shock)

• Death Mayo clinic, (2010). Dengue fever symptoms. Retrieved April 19, 2010 from

http://www.mayoclinic.com/health/dengue_fever/DS01028/DSECTION=symptoms

exotic viral infections and the liver

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