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Other non-viral pathogens

Chlamydial infections

Chlamydiae are a unique class of bacteria that are obligate intracellular parasites. Three Chlamydia species are recognised, all of which are human pathogens: C. trachomatis, C. pneumoniae and C. psittaci. The associated diseases, strains, mode of infection and host species are shown in Table 35.

Table 35. Characteristics of Chlamydia spp. and strains, modes of transmission and associated human diseases*

Species	Strains	Mode of transmission	Host species	Associated human diseases
C. trachomatis	LGV (L1, L2, L3)	Sexual	Humans	Lymphogranuloma venereum
	Trachoma (A,B,Ba,C)	Hand to eye, fomites, flies	Humans	Ocular trachoma
	Trachoma (B,Ba,D-K)	Sexual, hand to eye, neonatal	Humans	Ocular and genital disease, infant pneumonia
C. psittaci	Many	Aerosol	Birds, sheep, cats etc	Ornithosis (psittacosis)
C. pneumoniae	'TWAR'	Not defined aerosol?	Humans	Bronchitis, pneumonia

*Adapted from reference 44

Reports of chlamydial infections to LabVISE are shown in Table 36.

Table 36. Laboratory reports to LabVISE of chlamydial infections, 1991 to 2000

Organism	1991	1992	1993	1994	1995	1996	1997	1998	1999	2000	Total
Chlamydia trachomatis A-K	59	11	-	1	1	1	1	-	1	-	75
Chlamydia trachomatis L1-L3	18	-	-	-	-	-	1	-	-	-	19
Chlamydia trachomatis not typed	2,615	2,563	2,835	2,178	2,579	3,803	3,980	3,158	3,295	3,154	30,160
Chlamydia pneumoniae	2	14	1	-	2	1	3	-	2	36	61
Chlamydia psittaci	139	97	74	114	176	62	51	70	78	102	963
Chlamydia spp. typing pending	1	10	9	10	6	1	7	-	1	-	45
Chlamydia species not typed	-	6	18	62	75	54	28	57	21	8	329
Total	2,834	2,701	2,937	2,365	2,839	3,922	4,071	3,285	3,398	3,300	31,652

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Chlamydia trachomatis

Notifications of Chlamydial trachomatis infection between 1991 and 2000 to the NNDSS and laboratory reports to LabVISE are shown in Table 37.

Table 37. Laboratory reports to LabVISE and notifications to NNDSS of Chlamydia trachomatis infections, 1991 to 2000

Surveillance system	1991	1992	1993	1994	1995	1996	1997	1998	1999	2000
LabVISE	2,692	2,574	2,835	2,179	2,580	3,804	3,982	3,158	3,296	3,154
NNDSS	4,044	6,293	6,500	6,450	6,398	8,445	9,242	11,339	14,082	16,853

The NNDSS case definition for chlamydial infections requires the isolation of Chlamydia trachomatis or demonstration of chlamydial antigens in clinical specimens. For most of the study period and from most jurisdictions, notifications to the NNDSS of chlamydial infections were restricted to genital chlamydial infections. New South Wales did not start reporting chlamydial infections to the NNDSS until 1998. LabVISE laboratory reports have fallen from representing two-thirds of the NNDSS reports in 1991 to just 19 per cent in 2000. Whether laboratory reports in LabVISE were from clinical samples only from genital sites or whether they include samples from other infected sites cannot be determined.

The distribution of chlamydial infections by age and sex, reported to LabVISE are shown in Figure 20. The distribution is very similar to that seen in NNDSS notifications, with a female predominance (male to female ratio of 1:1.6) and the largest number of reports (57%) from young adults aged 15-24 years.

Figure 20. Laboratory reports to LabVISE of Chlamydia trachomatis infection, 1991 to 2000, by age and sex

Chlamydia psittaci

Notifications of Chlamydia psittaci infection between 1991 and 2000 to the NNDSS and laboratory reports to LabVISE are shown in Table 38.

Table 38. Laboratory reports to LabVISE and notifications to NNDSS of Chlamydia psittaci infections (ornithosis), 1991 to 2000

Surveillance system	1991	1992	1993	1994	1995	1996	1997	1998	1999	2000
LabVISE	139	97	74	114	176	62	51	70	78	102
NNDSS	136	98	94	86	186	86	35	64	84	100

Ornithosis has not been a notifiable disease in all Australian jurisdictions during the period 1991 to 2000 and consequently cases reported to the NNDSS do not represent national figures. While no agreed national NNDSS definition for ornithosis was used in this period, probable cases diagnosed based on an acute clinical illness compatible with ornithosis, were included. Laboratory diagnosis is based on increases in specific antibody titres, or more recently, detection of C. psittaci by nucleic acid tests.

For a number of years, LabVISE reported more cases of ornithosis than the NNDSS. LabVISE reports showed a male predominance (male to female ratio 1.7:1) and a peak of reports from adult men aged 50-54 years. Figure 21 shows the age and sex distribution of laboratory reports of ornithosis to LabVISE. This age and sex distribution is similar to that found in notifications of ornithosis to NNDSS.

Figure 21. Laboratory reports to LabVISE of Chlamydia psittaci infections, 1991 to 2000, by age and sex



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Chlamydia pneumoniae

Chlamydia pneumoniae causes an acute respiratory disease similar to that caused by Mycoplasma. Infection is widespread and antibody prevalence is low in children, around 50 per cent in young adults and continues to be high into old age. Clinical disease is seen in all ages but most frequently in young adults.²⁴

Mycoplasma pneumoniae

Mycoplasma pneumoniae is the cause of mycoplasma pneumonia (or primary atypical pneumonia), that presents predominantly as a febrile lower respiratory infection or occasionally as a pharyngitis, bronchitis or pneumonia.²⁴ The disease is worldwide in distribution and may occur in all age groups with occasional epidemics in institutions and military recruits.

Laboratory reports to LabVISE of Mycoplasma between 1991 and 2000 are shown in Table 39.

Table 39. Laboratory reports to LabVISE, of Mycoplasma infections, 1991 to 2000

Organism	1991	1992	1993	1994	1995	1996	1997	1998	1999	2000	Total
Mycoplasma pneumoniae	381	1,580	1,760	820	334	1,009	1,640	1,285	1,125	686	10,620
Mycoplasma hominis	2	4	-	2	-	2	-	2	5	8	25
Total	383	1,584	1,760	822	334	1,011	1,640	1,287	1,130	694	10,645

Mycoplasma pneumoniae infections reported to LabVISE were most commonly reported in female children aged 5-9 years (male to female ratio 0.9:1, Figure 22).

Figure 22. Laboratory reports to LabVISE of Mycoplasma pneumoniae infections, 1991 to 2000, by age and sex



Mycoplasma pneumoniae reports show variation from year to year without a distinct seasonal peak (Figure 23).

Figure 23. Laboratory reports to LabVISE of Mycoplasma pneumoniae infections, 1991 to 2000, by month of report



Mycoplasma hominis is commonly isolated from the genitourinary tract (more commonly from women than men), the neonatal conjunctiva and peripartum blood. The organism is associated with cervicitis, vaginitis, conjunctivitis and peripartum sepsis.⁴⁵

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Rickettsia

Coxiella burnetii

The rickettsial pathogen Coxiella burnetii is the cause of an acute febrile disease with a variety of clinical presentations of variable severity and duration (Q fever). The disease is particularly associated with livestock workers. Notifications of Q fever to the NNDSS and laboratory reports of Coxiella burnetii to LabVISE between 1991 and 2000 are shown in Table 40.

Table 40. Laboratory reports to LabVISE and notifications to NNDSS of Coxiella burnetii infection (Q fever), 1991 to 2000

Surveillance system	1991	1992	1993	1994	1995	1996	1997	1998	1999	2000
LabVISE	240	270	552	345	167	208	259	137	221	101
NNDSS	595	543	889	664	466	554	580	560	518	573

The NNDSS case definition for Q fever⁴⁶ is based on serology or isolation of the organism from a clinical sample. The trends in laboratory reports to LabVISE are similar to trends in NNDSS data, with a peak in reports in 1993 and lower reports in more recent years as a result of Q fever vaccine initiatives among abattoir workers, who are at high risk of contracting the disease.

An age, sex analysis of Coxiella burnetii infections shows a large male predominance (male:female ratio 5.2:1), similar to that shown in NNDSS data. The largest numbers of laboratory reports to LabVISE were from men aged 25-29 years (Figure 24).

Figure 24. Laboratory reports to LabVISE of Coxiella burnetii infections, 1991 to 2000, by age and sex



Small numbers of laboratory reports of other Rickettsia were sent to LabVISE during the period as shown in Appendix 3.

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Other pathogens

From 1992 to 1996 and in 1999 and 2000, several hundred reports were made to LabVISE of group A streptococci. While streptococcal group A infections have declined dramatically in Australia, Indigenous Australians in northern Australia continue to suffer endemic infection with corresponding high rates of rheumatic fever,⁴⁷ acute post-streptococcal glomerulonephritis,⁴⁸ streptococcal pyoderma⁴⁹ and resulting chronic renal disease and rheumatic heart disease.

A significant number of reports to LabVISE during the period 1991 to 2000 were received for other pathogens under surveillance in the NNDSS (Appendix 2). These include isolations of Yersinia, Brucella, Bordetella, Legionella, Leptospira, Treponema and Echinococcus. Since data on these pathogens was collected sporadically over the period and represent only a small fraction of notified cases reported to NNDSS, no analysis has been attempted here. Similarly for small numbers of reports of Cryptococcus, Entamoeba histolytica and Toxoplasmosis gondii no meaningful comments can be offered.

The reader is referred to NNDSS annual reports published in Communicable Diseases Intelligence for detailed analysis of the epidemiology of these and other pathogens in Australia.


This article was published in Communicable Diseases Intelligence Volume 26, No 3, September 2002