Outbreak of Anthrax among humans and cattle in Western province of Zambia, November 2016 to January 2017

N Kasese-Chanda1, B Mulubwe1, F Mwale1

  1. Ministry of Health, Directorate of Public health, Lusaka, Zambia

Correspondence: Nancy Kasese-Chanda (kasesechanda@gmail.com)

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Kasese-Chanda N, Mulubwe B, Mwale F. Outbreak of Anthrax among humans and cattle in Western province of Zambia, November 2016 to January 2017. Health Press Zambia Bull. 2017;1(1), pp50-55

An outbreak of anthrax occurred in Western province on 11th November 2016. The outbreak was confirmed using PCR.  Out of the 7 specimens examined for Bacillus anthracis, 3 were positive.  Altogether 67 suspected cases were investigated out of which one death (1.5%) was reported.  Over half of the cases were of age 15 years or older (56.1%) and males (56.7%).  Four peaks were identified on the epidemiologic curve suggesting multiple sources of infection.  Factors associated with the outbreak included: animal movement, belief that all the dead animals have to be eaten ‘there is no grave for animals’ and animals on loan (mafisa) cannot be disposed of without owners’ approval, hunger land low levels of animal vaccination coverage.  In conclusion, disposal of carcasses should be done by burning and burying followed by decontamination. Certificates should be issued to show that disposal was conducted by government.  Anthrax vaccines should be given to farmers free of charge through Ministry of Livestock and Fisheries.


Introduction

Outbreaks of anthrax have been documented in Zambia affecting humans as well as wild and domestic animals. The disease, caused by Bacillus anthracis, has been reported in wildlife such as hippo and buffalo and among cattle [1,2]. There are three types of anthrax in humans: cutaneous, gastrointestinal, and pulmonary: cutaneous being the most common form. Humans generally acquire the disease from infected animals as a result of handling the animal carcass or ingestion of its meat. Anthrax is not known to be transmitted from person to person [3]. It continues to be reported from many countries in domesticated and wild herbivores, especially where livestock vaccination programmes are inadequate or have been disrupted [4].

Anthrax outbreaks continue to occur globally, more commonly in sub-Saharan Africa, Asia and Central and South America [4]. Zambia has experienced more recently in 2016 two anthrax outbreaks affecting humans and animals in Muchinga and Western provinces [2,5]. The objectives for the current outbreak investigation were to assess: the extent of the outbreak; effectiveness of the interventions in mitigating the outbreak; and determine the needs required to mitigate the outbreak effectively and efficiently.  

Methods

The investigation was conducted in Western Province, one of the 10 provinces of Zambia, is located 22 degrees and 25.30 degrees east and 13.45 degrees and 17.45 degrees south. It has an area of 126 386-sq kilometres (16.8% of the total land of Zambia). It has 16 districts, five of which share an international boundary with Angola, while two districts share a boundary with Namibia. The poverty level in the province is at 80.4% (LCMS 2010). The province has varied communication challenges, with limited phone facilities in health centres, and poor road network posing limited abilities in referrals and challenges.  The outbreak occurred in four districts of the Western province: Shang’ombo, Nalolo, Limulunga and Kalabo (Figure 1).

 Figure 1 District with suspected anthrax cases in Western province

According to International Strategy for Disaster Reduction ISDR technical Guidelines of Zambia, anthrax is a notifiable disease with one case constituting an outbreak. WHO and CDC [6] defined a suspected case of anthrax as any person with acute onset characterized by several clinical forms that are:  (a)  cutaneous form: any person with skin lesion evolving over 1 to 6 days from a papular through a vesicular stage, to a depressed black eschar invariably accompanied by oedema that may be mild to extensive ; or (b)  gastro-intestinal: any person with abdominal distress characterized by nausea, vomiting, anorexia and followed by fever; or (c)  pulmonary (inhalation): any person with brief prodrome resembling acute viral respiratory illness, followed by rapid onset of hypoxia, dyspnea and high temperature, with X-ray evidence of mediastinal widening ; and has eaten and / or handled meat of a suspected or known confirmed case of anthrax in a human was defined as a clinically compatible case of cutaneous, inhalational or gastrointestinal illness that is laboratory-confirmed by isolation of B. anthracis from an affected tissue or site; or other laboratory evidence of B. anthracis infection.

Data were collected using data reviews, interviews, meetings with various stakeholders and field visitations. Case records from health facilities were reviewed age, sex, physical address and day of onset. Various stakeholders including health facility staff, veterinary assistants, agricultural field officers and community health committee members were interviewed. Meetings were also held with the district commissioners, district health officers, veterinary officers at the district and provincial level.  The University of Zambia School of Veterinary Medicine confirmed the presence of Bacillus anthracis by Polymerase chain reaction (PCR).

Results

The outbreak was first reported on 11th November, 2016 with the index case being a male farmer, from Shang’ombo, Western province.  Altogether 67 cumulative cases as at 19th January 2017 were investigated with Kalabo reporting most of the cases (31). Overall, one death (1.5%) was reported.  In Kalabo, the estimate case fatality rate during the period 11th November to 19th January was 3.2% among 31 suspected cases.  Table 1 shows the distribution of suspected cases of anthrax by district as at 19th January 2017.

Figure 2 shows an Epi-curve for the 4 districts affected by anthrax 11-November 2016 – 19 January 2017. There are four peaks: one between 27-30 November 2016, one on 22nd December 2016, another one between 29 December 2016 and 1st January 2017 and the last one on 9th January 2017.

Figure 2 Epi-curve for the 4 districts affected by anthrax 11-November 2016 – 19 January 2017

The distributions of suspected anthrax cases by age, sex and district are shown in Table 2.  Over half of the cases were of age 15 years or older (56.1%) and males (56.7%).  These findings are shown in Table 2. Out of the 7 specimens examined for Bacillus anthracis, 3 were positive.

Factors associated with anthrax

The following were factors hypothesized to be contributing to the continued spread of the disease: (a) Animal movement: (b) Disposal of dead animals: (c) Poverty: (d) Lack of vaccination:  

Discussion

The current anthrax outbreak in Western province was confirmed using PCR.  The epidemiologic curve suggests an active transmission of the disease throughout the period with multiple sources of infection.  Persons most affected were of age 15 years or older and were males.  The risk group for acquiring anthrax of skinning and butchering cattle that could have died of anthrax are usually older males.  On a smaller scale, this subpopulation of inhabitants of Western province is also involved in tanning the cattle hides and making stools and mats using them. While, health education intervention should be implemented to the entire population, older men should also be specifically targeted in order to curtail anthrax epidemics should they occur in Western Province.  Women may have been infected whilst preparing infected meat for drying or cooking.  Meanwhile, the younger age groups could have been infected by eating under-cooked infected meat.
In conclusion, disposal of carcases should be done by burning and burying followed by decontamination. Loaning of animals presented a problem of disposal as owners were not available.  Issuing of certificates should be made to show that disposal was conducted by government.  Anthrax vaccines should be given to farmers free of charge through Ministry of Livestock and Fisheries.The outbreak of anthrax in Western Province has persisted despite community sensitization messages in an area endemic for anthrax where the community should know better, suggesting need for targeted interventions. The results presented are limited in that both bivariate and multivariate analysis of risk factors associated with anthrax cases was not done. However, we hypothesize that animal movement, disposal of dead animals, poverty and lack of vaccination in cattle are factors all associated with the occurrence of anthrax outbreak in the affected districts. There is an animal transportation corridor from Shangombo to Mongu as a result pasture contamination is possible as animals move from one place to the other. The community hold a belief that all the dead animals have to be eaten ‘there is no grave for animals’ and animals on loan (mafisa) cannot be disposed of without owners’ approval. Additionally, an agriculture officer reported that mainly people are eating mango mixed with some mealie meal. Relish is rarely found and this could be one reason why they are opting to eat risk meat from diseased animals. Finally, less than 5% of cattle are vaccinated against anthrax in the Province. Anthrax is still classified as a management disease and therefore it is the owner of animals who is to ensure that animals are vaccinated. This has proved not effective as seen from the coverage of vaccinated animals even though the cost of vaccination is as low as K2 ($0.2) per animal.

Acknowledgments

We thank the following who responded to our questions and provided information in this report: Western PHO, Kalabo DHO, Limulunga DHO, Numa RHC staff and Community members in the affected districts.   

References

1.MOH. Mission report on technical support for anthrax outbreak in Chama district, Eastern province. Unpublished report submitted to the Ministry of Health, Lusaka, Zambia, 2011.

2.MOH Directorate of Public health. Anthrax outbreak in Muchinga. Unpublished report submitted to the Ministry of Health, Lusaka, Zambia, 2016.  

3.CDC. Anthrax (Bacillus anthracis) 2010 Case Definition. URL: https://wwwn.cdc.gov/nndss/conditions/anthrax/casedefinition/2010/

4.World Organization for Animal Health, World Health Organization, Food and Agriculture Organization of the United Nations. Anthrax in humans and animals. 4th edition. World Health Organization, 2008. URL: http://www.who.int/csr/resources/publications/anthrax_w eb.pdf.

5.Herriman R. Anthrax outbreak linked to tainted hippo meat more than doubles in Zambia. URL: http://outbreaknewstoday.com/anthrax-outbreak-linkedto-tainted-hippo-meat-more-than-doubles-in-zambia26869/.

6.IDSR technical Guidelines Zambia. Lusaka: Ministry of Health, 2011.

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