Research and analysis

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

Updated 29 February 2024

Applies to England

Background

This quarterly report is produced by the Emerging Infections and Zoonoses team in the Travel Health, Zoonosis, Emerging Infections, Respiratory and TB Division, Clinical and Emerging Infections Directorate, UK Health Security Agency (UKHSA).

Previous reports presenting data for both England and Wales can be found elsewhere on the GOV.UK website.

The report summarises laboratory-confirmed (and probable for leptospirosis) cases of selected zoonoses reported in England between October and December 2023 (fourth 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 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 Q4 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	Q4 2023 (note 1)	Total 2023 (note 1)
Anthrax (Bacillus anthracis)	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0
Brucellosis (Brucella spp.) (note 2)	1	2	3	1	7	1	3	4	5	13	2	7	9
Hepatitis E	351	350	276	300	1,277	322	397	343	457	1,519	378	383	408	332	1,501
Leptospirosis (Leptospira spp.)	7	5	16	26	54	4	10	26	12	52	5	8	33	24	70
Lyme disease (Borrelia burgdorferi)
All cases	133	240	637	263	1,273	158	244	578	273	1,253	158	252	906	335	1,651
Acute infections	62	151	530	196	939	102	193	442	185	922	87	182	701	174	1,144
Pasteurellosis (Pasteurella spp.)	158	209	196	145	708	173	214	230	184	801	151	222	255	184	812
C. psittaci / C. abortus	2	1	1	1	5	0	0	0	1	1	4	0	1	1	6
Toxoplasmosis (Toxoplasma gondii) (note 3)	46	50	39	52	187	54	37	57	45	193	63	54	56	55	228

Note 1: Provisional data.

Note 2: Data for Quarter 4 has not been included in this report due to an ongoing review of recent results, being done in collaboration with the reference laboratory. This data will be published once the review is complete.

Note 3: 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 332 laboratory-reported cases of HEV infection in the fourth quarter of 2023. 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 Q4 2023

Of the cases reported in the fourth quarter of 2023, 192 (58%) were male (aged 12 to 98 years, median 59 years), and 140 (42%) were female (aged 7 to 93 years, median 55.5 years) (see Table 2). The persisting observation of the predominance of middle age and older men (aged 45 and over) remains unexplained.

Table 2. Laboratory-confirmed cases of hepatitis E in England by age group and sex, Q4 2023

Age group	Male	Female	Total
0 to 14	3	1	4
15 to 24	9	19	28
25 to 44	42	29	71
45 to 64	65	44	109
Over 64	73	47	120
Total	192	140	332

In 2023, there were 1,501 laboratory-reported cases of HEV infection: 640 were female (aged 7 to 96, median 56 years), 860 were male (aged 9 to 100, median 59 years), there was one case where sex was unknown.

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 24 confirmed cases and 24 probable cases of leptospirosis reported in the fourth quarter of 2023, compared with 12 confirmed and 35 probable cases reported in the same quarter of 2022. Figure 2 shows the number of confirmed and probable 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 Q4 2023

In the fourth quarter of 2023, 19 (79%) confirmed cases were male (aged 18 to 80 years, median 47 years) and 5 (21%) were female (aged 25 to 63 years, median 45 years). Cases were reported in Yorkshire and Humber (n=7), the North West (n=5), West Midlands (n=4), South East (n=3), South West (n=3) and the London region (n=2).

Table 3. Laboratory-confirmed cases of leptospirosis in England by age group and sex, Q4 2023

Age group	Male	Female	Total
0 to 14	0	0	0
15 to 24	2	0	2
25 to 44	6	2	8
45 to 64	7	3	10
Over 64	4	0	4
Total	19	5	24

Of the confirmed cases, 6 reported recent travel abroad to: Southeast Asia (n=2), North Africa (n=1), Eastern Europe (n=1), Central America (n=1) and an unspecified destination in one case. The reported country of recent travel does not necessarily reflect where the infection was acquired.

Of the 24 confirmed cases, 9 reported potential exposures linked to a water source: 2 cases reported potential exposure through water sports, 2 cases reported exposure to canals, one case reported exposure to flood water, one case reported wild swimming and 3 reported unspecified water contact. Of the 24 confirmed cases, 3 reported potential exposures linked to rats.

There were 70 confirmed cases and 68 probable cases of leptospirosis reported in 2023. Of the 70 confirmed cases, 62 were male (aged 16 to 80, median 46.5 years) and 8 were female (aged 9 to 63, median 36.5 years).

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 fourth quarter of 2023 (n= 335) was higher than in the same time period in 2022 (n= 273). The total number of acute cases reported was lower in the fourth quarter of 2023 (n= 174) compared to the same period in 2022 (n= 185). 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 are 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 Q4 2023

Of the total cases reported in the fourth quarter, 174 (52%) were acute (including 14 with neurological Lyme disease) and 161 (48%) were longstanding. Of the acute cases, 82 were male (aged 8 to 78 years, median 46.5 years), 92 were female (aged 6 to 79 years, median 47.5 years). Table 4 shows the age group and sex distribution.

Table 4. Laboratory-confirmed acute cases of Lyme disease in England by age group and sex, Q4 2023

Age group (years)	Male	Female	Unknown	Total
0 to 14	4	2	6
15 to 24	5	3	8
25 to 34	9	17	26
35 to 44	21	19	40
45 to 54	13	18	31
55 to 64	16	19	35
65 to 74	10	10	20
Over 74	4	4	8
Total	82	92	174

The regions that reported the most acute cases in the fourth quarter of 2023 were London (n= 47), the South East (n= 42), and the South West (n= 31) (Table 5). 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 174 acute cases in the fourth quarter of 2023, 3 reported foreign travel, one case reported travel to Europe, one case reported travel to Africa, and one case reported recent travel to North America and Europe.

Of the total cases reported in the 2023, 1,144 (69%) were acute (including 80 with neurological Lyme disease) and 507 (31%) were longstanding. Of the acute cases, 548 were male (aged 1 to 86 years, median 47 years), 594 were female (aged 1 to 88 years, median 47 years), and there were 2 cases where sex was unknown (mean age 55.5 years). Of the 1,144 acute cases in 2023, 21 reported foreign travel.

Table 5. Laboratory-confirmed acute cases of Lyme disease in England by centre, Q1 2022 to Q4 2023

UKHSA centre	Q1 2022	Q2 2022	Q3 2022	Q4 2022	Total 2022	Q1 2023	Q2 2023	Q3 2023	Q4 2023	Total 2023
East Midlands	4	1	1	3	9	1	0	13	1	15
East of England	4	12	23	17	56	2	5	26	7	40
London	23	34	74	40	171	19	36	147	47	249
North East	2	2	18	7	29	4	2	22	10	38
North West	13	20	35	19	87	12	12	68	21	113
South East	22	59	133	44	258	23	56	167	42	288
South West	20	57	110	37	224	17	57	195	31	300
West Midlands	7	0	24	5	36	4	8	23	5	40
Yorkshire and Humber	6	8	24	13	51	5	6	40	10	61
Unknown	1	0	0	0	1	0	0	0	0	0
Total	102	193	442	185	922	87	182	701	174	1,144

Toxoplasmosis

Data for toxoplasmosis in England was obtained from the Toxoplasma Reference Unit (TRU, Public Health Wales Swansea). There were a total of 55 confirmed toxoplasmosis cases reported in the fourth quarter of 2023.

Figure 4. Laboratory-confirmed cases of toxoplasmosis in England by quarter, Q1 2019 to Q4 2023

Of the total confirmed cases, 15 (27%) were male (aged 10 to 72, median 29 years) and 40 (73%) were female (aged 0 to 81, median 32 years). Table 6 shows the age group and sex distribution.

Table 6. Laboratory-confirmed cases of toxoplasmosis in England by age group and sex, Q4 2023

Age group (years)	Male	Female	Total
Under 14	1	2	3
15 to 24	3	3	6
25 to 44	6	23	29
45 to 64	3	9	12
Over 65	2	2	4
Unknown	0	1	1
Total	15	40	55

There was a total of 228 confirmed toxoplasmosis cases reported in 2023. Of the total confirmed cases, 83 (36%) were male (aged 0 to 81, median 32 years) and 145 (64%) were female (aged 0 to 81, median 33 years).

Psittacosis

Data for C. psittaci / C. abortus 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 C. psittaci and 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 C. psittaci / C. abortus in the fourth quarter of 2023. In total, in 2023, there was a total of 6 reports of C. psittaci / C. abortus: 5 were male and one was female. Figure 5 shows the number of laboratory confirmed cases of C. psittaci / C. abortus between 2019 and 2023.

Figure 5. Laboratory-confirmed cases of psittacosis in England by quarter, Q1 2019 to Q4 2023

Other zoonotic organisms

There were 8 reports of Capnocytophaga spp. infection in the fourth quarter of 2023. Of the cases reported this quarter, 5 were further speciated to C. canimorsus. Of those speciated, 3 cases were male and 2 were female, and cases were reported in the South East (n= 1), North East (n= 1), West Midlands (n= 1), North West (n= 1), and South West (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. In 2023 there was a total of 70 reports of Capnocytophaga spp, of these cases 33 were female (aged 14 to 84, median 69 years) 37 were male (aged 18 to 83, median 72 years). Of the cases reported this quarter, 45 were further speciated to C. canimorsus. Of those speciated, 26 cases were male and 19 were female, and cases were reported in the South East (n= 12), South West (n= 8), Yorkshire and the Humber (n= 6), North East (n= 7), West Midlands (n= 4), East Midlands (n= 4), North West (n= 2), East of England (n= 1), and London (n= 1).

There was one report of Mycobacterium marinum infection in the fourth quarter of 2023. In 2023 there was a total of 18 cases of M. marinum, of these cases 2 were female (mean age 46 years) 16 were male (aged 30 to 80, median 64 years).

There were 2 reports of Erysipelothrix rhusiopathiae in the fourth quarter of 2023. Of the 2 cases reported this quarter, one was male and one was female. In 2023 there was a total of 11 cases of E. rhusiopathiae, of these cases 5 were female (aged 69 to 94 years) 6 were male (aged 0 to 83 years).

There were 4 reports of toxigenic Corynebacterium ulcerans infection in the fourth quarter of 2023. Of the cases reported this quarter, 3 were male and one was female. Three 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. In 2023 there was a total of 11 reports of C. ulcerans infection, 5 were male and 6 were female. Of these, 7 cases reported contact with companion animals.

There were 8 reports of Taeniasis in the fourth quarter of 2023. Of the cases reported this quarter, one was further speciated to T. saginata. In 2023 there was a total of 38 reports of Taeniasis, of these 10 were further speciated to T. saginata and 2 were T. solium.

There were no reports of Toxocariasis in the fourth quarter of 2023. In 2023 there was a total of 3 reports of Toxocariasis.