Research and analysis

Common animal-associated infections (England): third quarter 2023

Updated 29 February 2024

Applies to England

Background

This quarterly report is produced by the Emerging Infections and Zoonoses team in the Clinical and Emerging Infections Directorate, UK Health Security Agency (UKHSA). As of 2023, the data presented in these reports is for England only. Data for Wales will be reported separately by Public Health Wales. Previous reports presenting data for both England and Wales can be found on GOV.UK

The report summarises laboratory-confirmed (and probable for leptospirosis) cases of selected zoonoses reported in England between July and September 2023 (third quarter) and includes additional information on the quarterly trends for hepatitis E, leptospirosis, Lyme disease, toxoplasmosis and psittacosis.

It is important to note that not all cases will present to healthcare services, and cases may be treated empirically based on clinical suspicion without a confirmatory test. Therefore, the numbers in this report are expected to be an underestimate of the true burden of zoonotic disease in England, likely biasing towards severe infections as individuals with severe or symptomatic disease may be more likely to be tested. Furthermore, not all zoonoses presented in this report are notifiable in England. As such, it is likely not all confirmed laboratory test results are reported to UKHSA. For a list of notifiable diseases and causative organisms in England please see Notifiable diseases and causative organisms: how to report.

The impacts of the public health measures implemented in England due to the COVID-19 pandemic during 2020 and 2021 should be considered when making comparisons with this time period.

Data reported as provisional is subject to change due to late notifications and de-duplication.

The data presented in this report supersedes data in previous reports due to late notifications and de-duplication.

The regional data presented is based on the location of the referring hospital or laboratory and does not necessarily reflect the geographic area where the cases are located.

Q-fever data is not presented in this quarterly report. As part of an internal review, the data is being validated and will be published as soon as possible.

Overview

Table 1. Animal-associated infections in England: quarterly confirmed laboratory reports by specimen date, Q1 2021 to Q3 2023

Disease (organism)	Q1 2021	Q2 2021	Q3 2021	Q4 2021	Total (2021)	Q1 2022	Q2 2022	Q3 2022	Q4 2022	Total (2022)	Q1 2023	Q2 2023	Q3 2023*	Total (2023*)
Anthrax (Bacillus anthracis)	0	0	0	0	0	0	0	0	0	0	0	0	0	0
Brucellosis (Brucella spp.)	1	2	3	1	7	1	3	4	5	13	2	7	9	18
Hepatitis E	350	351	276	300	1,277	322	397	343	456	1,518	378	382	370	1,130
Leptospirosis (Leptospira spp.)	7	5	16	26	54	4	10	26	12	52	5	8	32	45
Lyme disease (Borrelia burgdorferi)
All cases	133	240	637	263	1,273	157	244	578	273	1,252	158	252	905	1,315
Acute infections	62	151	530	196	939	101	193	442	185	921	87	182	700	969
Pasteurellosis (Pasteurella spp.)	161	214	196	145	716	173	214	230	184	801	151	222	251	624
Psittacosis (C. psittaci / C. abortus)	2	1	1	1	5	0	0	0	1	1	4	0	1	5
Toxoplasmosis (Toxoplasma gondii)**	46	50	39	52	187	54	37	57	45	193	63	54	56	173

*Provisional data.

**Based on date specimen received.

Hepatitis E

The national hepatitis E virus (HEV) surveillance reports reference laboratory data (Public Health Laboratory Birmingham and the UKHSA Blood Borne Virus Unit Colindale) together with additional cases reported by local laboratories through the Second Generation Surveillance System (SGSS). The combined data sets provide a more accurate reflection of the number of acute HEV cases reported in England.

There were 370 laboratory-reported cases of HEV infection in the third quarter of 2023. This is a 7.9% increase compared with 343 cases reported in the same quarter of 2022. Figure 1 shows the number of HEV infections by quarter between 2019 and 2023. The data shows a decrease in the third quarter of 2021 and a gradual increase in cases between the third quarter of 2021 and the third quarter of 2023, with a peak in cases reported in quarter 4 of 2022.

Figure 1. Laboratory-confirmed cases of hepatitis E in England by quarter, Q1 2019 to Q3 2023

Of the cases reported in the third quarter of 2023, 220 (59.5%) were male (aged 9 to 89 years, median 59 years), and 150 (40.5%) were female (aged 7 to 88 years, median 55 years) (see Table 2). The persisting observation of the predominance of middle age and older men (aged 45 years and over) remains unexplained.

Table 2. Laboratory-confirmed cases of hepatitis E in England by age group and sex, Q3 2023

Age group	Male	Female	Total
0 to 14	3	5	8
15 to 24	5	15	20
25 to 44	55	35	90
45 to 64	75	49	124
Over 64	82	46	128
Total	220	150	370

Leptospirosis

Data for leptospirosis was obtained from the Rare and Imported Pathogens Laboratory (RIPL, UKHSA Porton). As of 1 August 2020, a laboratory-confirmed case of leptospirosis is defined by a positive 16S ribosomal ribonucleic acid (rRNA) polymerase chain reaction (PCR) result only. An Immunoglobulin M (IgM) enzyme-linked immunoabsorbent assay (EIA) continues to be performed on all samples of suspected leptospirosis cases. A case with a positive leptospirosis IgM result will usually be treated clinically on the basis of this result, even in the absence of a positive PCR result. A case with a positive IgM but without a confirmatory PCR result is therefore reported as a probable case for surveillance purposes. National surveillance of probable cases of leptospirosis was introduced in 2021.

There were 32 confirmed cases and 21 probable cases of leptospirosis reported in the third quarter of 2023, compared with 26 confirmed and 30 probable cases reported in the same quarter of 2022. Figure 2 shows the number of confirmed cases reported by quarter over the past 5 years (2019 to 2023).

Figure 2. Laboratory-confirmed cases of leptospirosis in England by quarter, Q1 2019 to Q3 2023

In the third quarter of 2023, 30 (94%) confirmed cases were male (aged 16 to 77 years) and 2 were female (median 22 years). Cases were reported in the London region (n=7) and in the North West (n=6), South West (n=5), South East (n=4), Yorkshire and Humber (n=3), East Midlands (n=2), East of England (n=2), West Midlands (n=2) and North East (n=1).

Of the confirmed cases, 13 reported recent travel abroad, to: South East Asia (n=4), South Asia (n=2), Western Europe (n=3), and South America (n=4). The country of recent travel does not necessarily reflect where the infection was acquired.

Of the 32 confirmed cases, 10 reported potential exposures linked to a water source: 5 cases reported wild swimming, 2 reported falling into water, and 3 reported unspecified water contact. Of the 32 confirmed cases, 3 reported potential exposures linked to rats.

Note: The number of probable cases of leptospirosis in 2023 was over-reported in previous publications due to an error in data processing. The data presented in this report supersedes data in previous reports.

Lyme disease

Data for Lyme disease was obtained from the Rare and Imported Pathogens Laboratory (RIPL, UKHSA Porton). The total number of confirmed Lyme disease cases reported in the third quarter of 2023 (n=905) was higher than in the same time period in 2022 (n=578). The total number of acute cases reported was higher in the third quarter of 2023 (n=700) compared to the same period in 2022 (n=442). It should be noted that diagnosis for acute Lyme disease presenting with erythema migrans (‘bullseye rash’) is made clinically and testing is not recommended, as per NICE guidelines. The number of laboratory-confirmed cases presented in this report is therefore likely an underestimate of the true burden of acute Lyme disease in England.

Figure 3 shows how the number of cases continues to peak during the summer months (third quarter), which corresponds to the peak period of exposure to ticks in the UK, the spring and summer months.

Figure 3. Laboratory-confirmed cases of Lyme disease in England by quarter, Q1 2019 to Q3 2023

Of the total cases reported in the third quarter, 700 (77.3%) were acute (including 33 with neurological Lyme disease) and 205 (22.7%) were longstanding. Of the acute cases, 329 were male (aged 4 to 86 years, median 49 years), 347 were female (aged 1 to 88 years, median 49 years) and 24 were unknown (aged 1 to 75 years, median 51.5 years). Table 3 shows the age group and sex distribution.

Table 3. Laboratory-confirmed acute cases of Lyme disease in England by age group and sex, Q3 2023

Age group (years)	Male	Female	Unknown	Total
0 to 14	37	30	1	68
15 to 24	22	17	1	40
25 to 34	29	52	1	82
35 to 44	58	54	5	117
45 to 54	55	52	4	111
55 to 64	75	74	9	158
65 to 74	35	47	1	83
Over 74	18	21	1	40
Unknown	0	0	1	1
Total	329	347	24	700

The regions that reported the most acute cases in the third quarter of 2023 were the South West (n=195), the South East (n=167) and London (n=146) (Table 4). This data is based on the location of the referring hospital or laboratory and does not necessarily reflect the geographic area where the tick bite occurred. Of the 700 acute cases in the third quarter of 2023, 22 reported foreign travel, specifically to North America (n=5), Eastern Europe (n=4), Scandinavia (n=4), Western Europe (n=3), the Balkans (n=3), Africa (n=2) and Southern Europe (n=1),

Table 4. Laboratory-confirmed acute cases of Lyme disease in England by centre, Q1 2022 to Q3 2023

UKHSA centre	Q1 2022	Q2 2022	Q3 2022	Q4 2022	Total 2022	Q1 2023	Q2 2023	Q3 2023	Total 2023
East Midlands	4	1	1	3	9	1	0	13	14
East of England	4	12	23	17	56	2	5	26	33
London	23	34	74	40	171	19	36	146	201
North East	2	2	18	7	29	4	2	22	28
North West	13	20	35	19	87	12	12	67	91
South East	22	59	133	44	258	23	56	167	246
South West	20	57	110	37	224	17	57	195	269
West Midlands	7	0	24	5	36	4	8	24	36
Yorkshire and Humber	6	8	24	13	51	5	6	40	51
Unknown	1	0	0	0	1	0	0	0	0
Total	102	193	442	185	922	87	182	700	969

Note: The number of Lyme disease cases between 2019 and 2023 was under-reported in previous publications due to a change in the data processing method involving date assignment. This change has now been reflected in this publication and historical data has now been corrected. The data presented in this report supersedes data in previous reports.

Toxoplasmosis

Data for toxoplasmosis in England was obtained from the Toxoplasma Reference Unit (TRU, Public Health Wales Swansea). There were a total of 56 confirmed toxoplasmosis cases reported in the third quarter of 2023, which is similar to the same quarter of 2022 (n=57).

Figure 4. Laboratory-confirmed cases of toxoplasmosis in England by quarter, Q1 2019 to Q3 2023

Of the total confirmed cases, 26 (46%) were male (aged 9 to 77, median 35 years) and 30 (54%) were female (aged 1 to 65, median 36 years). Table 5 shows the age group and sex distribution.

Table 5. Laboratory-confirmed cases of toxoplasmosis in England by age group and sex, Q3 2023

Age group (years)	Male	Female	Total
Under 14	2	1	3
15 to 24	4	0	4
25 to 44	12	21	33
45 to 64	6	7	13
Over 65	2	1	3
Total	26	30	56

Psittacosis

Data for psittacosis was obtained from the Respiratory and Vaccine Preventable Bacteria Reference Unit (RVPBRU) in Colindale and from cases reported by local laboratories through the Second Generation Surveillance System (SGSS). As of 1 January 2023, a confirmed case of psittacosis is defined by a positive 16S rRNA PCR result or culture isolation only.

It should be noted that the existing PCR assay is unable to differentiate between Chlamydia psittaci (C. psittaci) and Chlamydia abortus (C. abortus). However, as there are currently no other reliable methods of psittacosis identification, the numbers presented in these reports will reflect laboratory-confirmed cases with a positive PCR result for C. psittaci and C. abortus.

There was one report of psittacosis in the third quarter of 2023. There were no reports in the same quarter of 2022. Figure 5 shows the number of laboratory-confirmed cases of psittacosis between 2019 and 2023.

Figure 5. Laboratory-confirmed cases of psittacosis in England by quarter, Q1 2019 to Q3 2023

Other zoonotic organisms

There were 25 reports of Capnocytophaga spp. infection in the third quarter of 2023. This is lower than the number reported in the same quarter of 2022 (n=46). Of the cases reported this quarter, 16 were further speciated to C. canimorsus. Of those speciated, 12 were male and 4 were female, and cases were reported in the South East (n=4), Yorkshire and Humber (n=4), North East (n=3), East Midlands (n=2), West Midlands (n=1), North West (n=1) and London (n=1). Capnocytophaga spp. are frequently carried in the mouths of companion animals (cats and dogs) or humans, and may be associated with an animal or human bite or opportunistic infections in those with impaired immune systems.

There were 2 reports of Mycobacterium marinum infection in the third quarter of 2023. This is a decrease compared to the number reported in the same quarter in 2022 (n=4). Of the 2 cases reported this quarter, one was male and one was female.

There were 5 reports of Erysipelothrix rhusiopathiae in the third quarter of 2023. This is an increase compared to the number reported in the same quarter of 2022 (n=3). Of the 5 cases reported this quarter, 3 were female and 2 were male.

There were 3 reports of toxigenic Corynebacterium ulcerans infection reported in the third quarter of 2023. This is less than the number of cases reported in the same quarter of 2022 (n=4). Of the cases reported this quarter, 1 was male and 2 were female, and all cases were aged above 60 years. Two cases reported contact with companion animals. In England, contact with companion animals remains the most frequently reported exposure for individuals with confirmed toxigenic C. ulcerans infections. However, the animals may not show evidence of infection and it is not always possible to confirm the carriage of C. ulcerans in animals.

There were 7 reports of Taeniasis in the third quarter of 2023. This is a decrease compared to 8 cases reported in the same quarter of 2022. Of the cases reported this quarter, one was further speciated to T. saginata.

There was one report of Toxocariasis in the third quarter of 2023. There were no reports in the same quarter of 2022.