Sunday, October 1, 2023
| Characteristic† | All patients, no. (%), n = 357‡ |
UK-born patients, no. (%), n = 214§ |
Non–UK-born patients, no. (%), n = 83¶ |
|---|---|---|---|
| Age group, y | |||
| 0–14 | 6 (1.7) | 4 (1.9) | 2 (2.4) |
| 15–44 | 106 (29.7) | 39 (18.2) | 54 (65.1) |
| 45–64 | 70 (19.6) | 45 (21.0) | 12 (14.5) |
| ≥65 | 175 (49.0) | 126 (58.9) | 15 (18.1) |
| Male sex | 196 (55.1) | 130 (60.8) | 37 (44.6) |
| Ethnicity | |||
| White | 230 (73.0) | 199 (93.9) | 15 (18.5) |
| Black African | 37 (11.8) | 2 (0.9) | 35 (43.2) |
| Indian subcontinent | 16 (5.1) | 3 (1.4) | 9 (11.1) |
| Other | 32 (10.2) | 8 (3.8) | 22 (27.2) |
| Time since entered United Kingdom, y | |||
| <2 | NA | NA | 10 (14.7) |
| 2–5 | NA | NA | 17 (25.0) |
| 6–10 | NA | NA | 20 (29.4) |
| >10 | NA | NA | 21 (30.9) |
| Place of residence | |||
| Rural | 86 (24.9) | 62 (29.0) | 9 (10.8) |
| Urban | 259 (75.1) | 152 (71.0) | 74 (89.2) |
| Pulmonary TB# | |||
| Yes | 199 (56.9) | 131 (61.5) | 38 (45.8) |
| No | 151 (42.3) | 82 (38.5) | 45 (54.2) |
| ≥1 social risk factor** | 12 (7.9) | 6 (5.9) | 5 (11.1) |
| Previous TB diagnosis | 17 (6.1) | 13 (6.7) | 5 (5.4) |
Table 1. Characteristics of patients with Mycobacterium bovis disease, England, Wales, and Northern Ireland, 2002–2014*
*IQR, interquartile range; NA, not applicable; TB, tuberculosis.
†Sex, age, and site of disease reported for all cases (excluding breakdowns by birth in or not in the United Kingdom); all other characteristics reported only for notified cases.
‡Median age (IQR) 58 (36–77) y.
§Median age (IQR) 70 (52–79) y.
¶Median age (IQR) 35 (28–58) y.
#Pulmonary TB with or without extrapulmonary TB, those recorded as “no” had exclusively extrapulmonary TB.
**Data only available from 2010 on.
| Characteristic |
M. bovis patients, no. (%), n = 329 |
M. tuberculosis patients, no. (%), n = 58,540 |
Univariable analysis | Multivariable analysis | ||
|---|---|---|---|---|---|---|
| OR (95% CI) | p value | OR (95% CI) | p value | |||
| Age group, y | ||||||
| 0–14 | 6 (1.8) | 1,200 (2.1) | 1.9 (0.8–4.3) | <0.001 | 1.5 (0.6–3.6) | <0.001 |
| 15–44 | 102 (31.0) | 38,558 (65.9) | Referent | Referent | ||
| 45–64 | 61 (18.5) | 10,953 (18.7) | 2.1 (1.5–2.9) | 1.3 (0.9–2.0) | ||
| ≥65 | 160 (48.6) | 7,826 (13.4) | 7.7 (6.0–9.9) | 3.6 (2.6–5.2) | ||
| Sex | ||||||
| M | 179 (54.4) | 33,715 (57.7) | 0.9 (0.7–1.1) | 0.229 | 0.9 (0.7–1.1) | 0.287 |
| F | 150 (45.6) | 24,721 (42.3) | Referent | Referent | ||
| UK-born | ||||||
| Yes | 214 (72.1) | 13,576 (24.7) | 7.9 (6.1–10.1) | <0.001 | 2.6 (1.7–4.1) | <0.001 |
| No | 83 (27.9) | 71,361 (75.3) | Referent | Referent | ||
| Ethnicity | ||||||
| White | 230 (73) | 11,968 (21.1) | 28.0 (16.8–46.4) | <0.001 | 14.6 (7.2–26.9) | <0.001 |
| Black African | 37 (11.8) | 12,501 (22.1) | 4.3 (2.4–7.7) | 7.4 (3.7–14.9) | ||
| Indian subcontinent† | 16 (5.1) | 23,285 (41.1) | Referent | Referent | ||
| Other | 32 (10.2) | 8,905 (15.7) | 5.2 (2.9–9.5) | 7.3 (3.6–14.8) | ||
| Occupation | ||||||
| Agricultural/animal contact work | 20 (7.9) | 116 (0.3) | 32.4 (19.8–53.0) | <0.001 | 29.5 (16.9–51.6) | <0.001 |
| Other | 232 (92.1) | 43,698 (99.7) | Referent | Referent | ||
| Site of disease | ||||||
| Pulmonary | 193 (58.8) | 37,580 (64.2) | 0.8 (0.6–1.0) | 0.048 | 0.4 (0.3–0.5) | <0.001 |
| Extrapulmonary only | 135 (41.2) | 20,938 (35.8) | Referent | Referent | ||
| Place of residence | ||||||
| Rural | 81 (24.6) | 1,944 (3.3) | 9.5 (7.3–12.2) | <0.001 | 2.8 (2.0–3.9) | <0.001 |
| Urban | 248 (75.4) | 56,380 (96.7) | Referent | Referent | ||
Table 2. Demographics and risk factors for patients with Mycobacterium tuberculosis and M. bovis disease, England, Wales, and Northern Ireland, 2002–2014*
*Interactions between 1) place of birth (UK-born/non–UK-born) and all of the other variables (age, sex, ethnicity, occupation, site of disease, place of residence [rural/urban]) and 2) age and site of disease or place of residence (rural/urban) were tested. No significant interactions existed in the model.
OR, odds ratio.
†Indian, Bangladeshi, and Pakistani ethnic groups.
| Exposure | No. characteristics/no. with information recorded (%) | ||
|---|---|---|---|
| All patients | UK-born patients | Non–UK-born patients | |
| Consumption of unpasteurized milk products | 109/166 (65.7) | 74/112 (66.1) | 25/37 (67.6) |
| In United Kingdom | 66/88 (75.0) | 60/64 (93.8) | 1/15 (6.7) |
| Travel or residence in a high incidence country | 77/203 (37.9) | 29/126 (23.0) | 44/56 (78.6) |
| Work related animal exposure | 51/103 (49.5) | 35/71 (49.3) | 7/22 (31.8) |
| In United Kingdom | 33/37 (89.2) | 28/29 (96.6) | 2/4 (50.0) |
| Contact with human patient with TB | 33/181 (18.2) | 21/120 (17.5) | 10/42 (23.8) |
| In United Kingdom | 36/38 (94.7) | 19/19 (100) | 6/8 (75.0) |
| Physical contact with wild animal | 18/126 (14.3) | 15/92 (16.3) | 0/25 (0) |
| In United Kingdom | 10/13 (76.9) | 7/10 (70.0) | Not applicable |
| Physical contact with animal with TB | 18/99 (18.2) | 14/76 (18.4) | 2/18 (11.1) |
| In United Kingdom | 10/1 (90.9) | 9/10 (90.0) | 1/1 (100) |
| Pet with TB† | 2 | 2 | 0 |
| Farm animal with TB† | 11 | 9 | 1 |
| No exposure† | 6 | 6 | 0 |
Table 3. Risk factor exposures reported by patients with Mycobacterium bovis disease, England, Wales, and Northern Ireland, 2006–2014*
*TB, tuberculosis.
†Denominator not available.
This activity is intended for infectious disease specialists, public health officials, internists, pulmonologists, and other clinicians caring for patients with or at risk for Mycobacterium bovis infection.
The goal of this activity is to describe the epidemiology of human cases of M bovis in England, Wales, and Northern Ireland from 2002-2014, based on a national cohort study.
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Despite control efforts, Mycobacterium bovis incidence among cattle remains high in parts of England, Wales, and Northern Ireland, attracting political and public health interest in potential spread from animals to humans. To determine incidence among humans and to identify associated factors, we conducted a retrospective cohort analysis of human M. bovis cases in England, Wales, and Northern Ireland during 2002–2014. We identified 357 cases and observed increased annual case numbers (from 17 to 35) and rates. Most patients were ≥65 years of age and born in the United Kingdom. The median age of UK-born patients decreased over time. For 74% of patients, exposure to risk factors accounting for M. bovis acquisition, most frequently consumption of unpasteurized milk, was known. Despite the small increase in case numbers and reduction in patient age, M. bovis infection of humans in England, Wales, and Northern Ireland remains rare.
After the 1960s, the number of human cases of tuberculosis (TB) caused by Mycobacterium bovis decreased significantly in England, Wales, and Northern Ireland, co-inciding with widespread implementation of milk product pasteurization and national bovine TB control programs.[1–3] During the past 2 decades in these 3 countries, an average of 30 cases of M. bovis in humans occurred annually; numbers decreased in the early 2000s before again increasing.[4–6] During the same period, incidence of M. bovis in cattle herds in parts of England, Wales, and Northern Ireland increased substantially but has now plateaued.[4,7–9]
M. bovis control[2,7,10,11] attracts political, public health, and media interest because of potential spread from animals to humans, effects on animal health and trade,[1] and the role of wildlife in the transmission cycle.[12] Highly visible interventions, including wildlife management to prevent transmission to livestock, are used to attempt to control M. bovis spread,[6,9,10] thereby protecting human health.
Compared with other countries in western Europe, the rate of TB among humans in the United Kingdom is high: 9.6 cases/100,000 population (6,240 cases) in 2015.[13] Most TB cases occurred in those born abroad, who probably acquired infection before entering the United Kingdom. Although only 1.1% (42 cases) of culture-confirmed TB cases were caused by M. bovis,[6] it remains a public health priority.
The drivers of the epidemiology of M. tuberculosis are well described.[13–15] However, there is comparatively less information on the sources of M. bovis in humans, other than the recognized risks of unpasteurized milk consumption and close contact with infected cattle.[1,3] We provide an update on the demographic characteristics of humans with M. bovis disease in England, Wales, and Northern Ireland.[16] To address the gap in knowledge regarding lesser known sources of acquisition, we describe the demographic and clinical characteristics of humans with TB caused by M. bovis compared with M. tuberculosis. In addition, we describe potential human exposures that may indicate M. bovis acquisition and include a genotyping comparison of the causative organisms.
