Page content: Victorian statutory requirement | Infectious agent | Identification | Incubation period | Public health significance and occurrence | Reservoir | Mode of transmission | Period of communicability | Susceptibility and resistance | Control measures | Outbreak measures | Additional sources of information

Victorian statutory requirement

Suspected or confirmed meningococcal infection (Group A disease) must be notified immediately by telephone or fax followed by a written notification within five days.

School exclusion: cases should be excluded until adequate carrier eradication therapy has been completed. Contacts do not need to be excluded if receiving carrier eradication therapy.

Infectious agent

Neisseria meningitidis (the meningococcus) is a gram-negative diplococcus. Various serogroups have been recognised including groups A, B, C, 29E, H, I, K, L, W135, X, Y and Z. Within these groups, certain serotypes have been identified, for example, group B serotypes 2b and 15. In 2004 groups B and C were the most common in Victoria.

Identification

Clinical features
Clinical features of meningococcal infection include an acute onset of meningitis or septicaemia. Typical features of these include fever, intense headache, nausea, vomiting and neck stiffness. There may be a petechial or purpuric rash on the trunk and limbs that may sometimes cover large areas of the body. In fulminating cases there is sudden prostration and shock associated with the characteristic rash and this condition has a high fatality rate. Chronic meningococcal septicaemia can also occur with febrile episodes, skin rashes and fleeting joint pains.

Method of diagnosis
Diagnosis is usually made on clinical grounds confirmed by laboratory tests. Laboratory tests include:

• gram stain of cerebrospinal fluid, skin lesion smear or joint fluid
• culture of blood, CSF or other sterile site
• polymerase chain reaction (PCR).

Meningococcal isolates from all cases of invasive disease should be sent to MDU at the University of Melbourne to ensure appropriate monitoring of serogroups and to perform susceptibility testing. This needs to be authorised by the Communicable Diseases Section of the Department of Human Services.

Incubation period

The incubation period is commonly three to four days, but can vary from two to seven days. People who do not develop the disease in the seven days after colonisation may become asymptomatic carriers.

Public health significance & occurrence

Invasive meningococcal infections occur in endemic and epidemic forms. In Australia epidemic disease has not occurred for many years. Endemic disease is at low levels of incidence and cases are generally unrelated to each other. Despite this, invasive meningococcal disease is of public health importance and is frequently a cause of public alarm and receives a high level of media attention.

Meningococcal disease characteristically has a seasonal pattern with a peak of incidence in the winter and spring months. Although the reasons for this seasonality are not clear, there is evidence that influenza virus or Mycoplasma pneumoniae infections may predispose to invasive disease and that closer personal contact or lack of ventilation may facilitate transmission of meningococci.

The three major serogroups of meningococci cause different patterns of disease. Serogroup A meningococci cause outbreaks of infection in areas such as the meningitis belt of Africa where the incidence of meningococcal infection rises sharply towards the end of the dry season and declines rapidly with the onset of rains. The epidemics occur in 8–14 year cycles. Since 1990 New Zealand has been experiencing an epidemic of serogroup B meningococcal disease. Age-standardised rates for Maori and Pacific Island people were three and six times higher respectively than for the European population. Serogroup C meningococci are usually associated with sporadic disease but can cause small or large outbreaks. Attack rates for serogroup C are between those seen with serogroups A and B.

Meningococcal disease has had cyclical peaks of incidence. Notification of ‘meningitis’ reached a peak of 33.1 cases per 100 000 in 1942 (2371 cases) as part of a pandemic of serogroup A disease during World War II. Apart from another peak of activity in the early 1950s, there was a steady decline of notifications to less than 0.5 cases per 100 000 in 1987. The notification rate for meningococcal disease to the National Notifiable Diseases Surveillance System (NNDSS) has been slowly increasing over the past 10 years from 1.6 per 100 000 in 1991 to 3.1 per 100 000 in 2000. In 2002 there were 129 notifications in Victoria (1/3 of the national total) of which 47 were serogroup B and 72 were serogroup C.

Reservoir

Human.

Mode of transmission

Respiratory droplets shed from the upper respiratory tract transmit meningococci from one person to another. Humans are the only natural hosts for meningococci and the organism dies quickly outside the human host. It is not able to be isolated from environmental surfaces or samples.

Salivary contact has in the past been regarded as a means of transmission of meningococci. There is little evidence to support this view. Available evidence indicates that neither saliva nor salivary contact is important in the transmission of meningococci. Saliva has been shown to inhibit the growth of meningococci. Carriage of meningococci has not been convincingly shown to be associated with saliva contact. A case-control study of United Kingdom university students found no association between carriage of meningococci and sharing of drinks or cigarettes and a weak association with ‘intimate kissing’ (OR = 1.4 & 95% CI, 1.0–1.8%).

It is unclear whether carriage in these circumstances is due to saliva contact rather than to droplets shed during household-like (close and prolonged) contact.

Period of communicability

It is communicable until the organisms are no longer present in discharges from the nose and mouth.

Susceptibility & resistance

Susceptibility to clinical disease is low as evidenced by the usual high ratio of carriers to cases. Susceptibility decreases with age although a secondary peak of meningococcal meningitis occurs in adolescents and young adults in the age group of 15–24 years. Patients deficient in certain complement components in the blood are prone to recurrent meningococcal infections. There is an increased and prolonged risk of secondary infections in close contacts. In one series, the incidence of such infection was 0.5% with a median interval of seven weeks between the index and secondary cases. Secondary cases have been reported up to five months later. The risk in household contacts is 500 to 800 times higher than in the general population.

There is no maternal immunity.

Control measures

Preventive measures
Note that most strains of meningococci do not cause disease, but instead provide protection. Other protective bacteria such as Lactamicas (Neisseria lactamica spp) also colonise the nasopharynx. By giving chemoprophylaxis when it is not needed these bacteria, which are protective, are also eradicated. People can carry meningococci with no ill effects for many months. Carriage produces protection. There is no evidence to suggest carriers will suddenly become cases after weeks or months of carriage.

Conjugate vaccines are available that can give long lasting protection against meningococcal serogroup C disease. There is no vaccine for meningococcal serogroup B disease. There is polysaccharide quadrivalent vaccine available in Australia against groups A, C, Y and W135 however it cannot be given under two years of age and only protects for one to five years. This vaccine is considered a ‘travel’ vaccine for travellers to epidemic and highly endemic areas such as Brazil, Mongolia, Vietnam, India, Nepal and sub-Saharan Africa and is a requirement for visits to Mecca.

There are different brands of (conjugate) meningococcal serogroup C vaccine available. The vaccines contain meningococcal serogroup C ‘sugars’ joined with an inactive protein of either diphtheria or tetanus toxoid and additives aluminium phosphate or hydroxide.

Under the National Immunisation Program, a single dose of meningococcal serogroup C vaccine is given at 12 months of age. If parents wish to purchase vaccine to immunise their child prior to 12 months of age, infants from six weeks to four months of age at the commencement of vaccination receive three doses one to two months apart. Babies from four months to 11 months at the commencement of vaccination receive two doses one to two months apart.

The National Meningococcal C Vaccination Program is a four year program from 2003–2006 in which all persons aged 1–19 years in 2003 are eligible for a dose of meningococcal C vaccine.

Control of case
Prompt treatment with parenteral penicillin in adequate doses should begin when a presumptive clinical diagnosis is made prior to laboratory confirmation. In cases with a very acute onset, such treatment should commence prior to transfer of the patient to hospital even though there may be some interference with laboratory confirmation by culture. Suitable alternatives for patients who are allergic to penicillin include ceftriaxone, cefotaxime or chloramphenicol.

Since penicillin only temporarily suppresses but does not eradicate the organisms in the nasopharynx, all patients should be treated with a drug such as rifampicin prior to discharge from hospital. If ceftriaxone is used in treatment rifampicin need not be given. Consult the current version of Therapeutic guidelines: antibiotic (Therapeutic Guidelines Limited).

Control of contacts
Meningococci are likely to have been acquired from an asymptomatic person (carrier) who either lives in the same household or is a sexual partner of the sick person. Children tend to acquire their disease from adults (in their household) whereas teenagers and adults are more likely to acquire their disease from close friends.

Clearance antibiotics should only be given to the following people (see below) who have had contact with the case seven days prior to the onset of the case’s illness. They should be commenced as soon as possible after diagnosis.

Contacts include:

• household contacts are defined as those people living in the same house and include recent visitors who stayed overnight in the seven days preceding the onset of the case’s illness
• dormitory contacts in boarding schools, military barracks, school camps, and hostels in the seven days preceding the onset of the case’s illness
• sexual (intimate) contacts
• medical, nursing, or paramedical staff that have performed mouth-to-mouth resuscitation or intubation or suction or similar intimate treatment with a case of meningococcal disease prior to being started on therapeutic antibiotics.

The risk of meningococcal disease in close contacts, whilst higher than the general population, is still very low. The risk is highest in the first seven days after a case and falls rapidly during the following weeks. If antibiotic prophylaxis is not given, the absolute risk to an individual in the same household one to 30 days after an index case is about one in 300. The increased risk in household members may be due to a combination of genetic susceptibility in the family, increased exposure to virulent meningococci and environmental factors.

Clearance antibiotics should only be given to those people who are at risk of either being the source of disease in the case, or of having acquired the invading organism from the case. The aim of clearance antibiotics is to prevent further transmission.

There are three antibiotics currently used for the chemoprophylaxis of meningococcal disease. Each agent has advantages and disadvantages and each is the preferred agent in specific circumstances.

Clearance antibiotic for contacts of meningococcal disease
Rifampicin can be dispensed for meningococcal prophylaxis as syrup for children or in capsules for older children and adults. The product information should be consulted for the adverse events and side effects of rifampicin, although it should be noted that the product information recommends a once-daily four-day regimen of rifampicin for the chemoprophylaxis of meningococcal disease. The two-day regimen (below) is recommended by the Communicable Diseases Network Australia.

*Rifampicin syrup contains 100 mg/5 mL

Ciprofloxacin: Adults 500 mg orally, single dose (minimum age 12 years and weight >40 kg). This is preferred in women taking the oral contraceptive pill. Although ciprofloxacin is not registered for chemoprophylaxis of meningococcal disease in Australia the Communicable Diseases Network Australia recommends it for that purpose.

Ceftriaxone: Adults 250 mg IM (recommended for pregnant contacts). This may be dissolved in lignocaine 1% solution to reduce pain at the injection site. Dosage for children (<12yrs) is 125 mg IM. Not for infants under 1 month of age.

Control of environment
Respiratory isolation is recommended for 24 hours after commencing treatment. There should be concurrent disinfection of discharges from nose or throat and articles soiled with such discharges. Articles used by the patient should be terminally cleaned.

Outbreak measures

When there are two or more cases in four weeks of exactly the same strain in a childcare centre, school or university, all students and staff in the same class or in the same group as the case will be given clearance antibiotics. If serogroup C disease is identified a vaccination campaign may be instituted.

Clusters of invasive meningococcal disease in people who have had a low level of salivary contact like footballers who have shared drink bottles or churchgoers who have shared a communion cup appear to be very rare. Although clusters have been described, for example, in association with sporting events and sports clubs, the reported details indicate that point-source salivary transmission was not involved. Secondary cases in situations where dribbling of saliva is common such as child day-care centres are also rare.

Additional sources of information

• Australian Government Department of Health and Ageing 2003, ‘Annual report of the Australian Meningococcal Surveillance Programme’, Communicable Diseases Intelligence, vol. 27, no. 2.
• Communicable Diseases Network Australia 2007, Guidelines for the early clinical and public health management of meningococcal disease in Australia.
• Victorian Department of Human Services, Advice for medical practitioners