An unusually long Rift valley fever inter-epizootic period in Zambia: Evidence for enzootic virus circulation and risk for disease outbreak.

Rift valley fever (RVF) is a mosquito-borne disease of animals and humans. Although RVF outbreaks are usually reported at 5-15-year intervals in sub-Saharan Africa, Zambia has experienced an unusually long inter-epizootic/-epidemic period of more than three decades. However, serological evidence of RVF virus (RVFV) infection in domestic ruminants during this period underscores the need for comprehensive investigation of the mechanisms of virus perpetuation and disease emergence. Mosquitoes (n = 16,778) captured from eight of the ten provinces of Zambia between April 2014 and May 2019 were pooled (n = 961) and screened for RVFV genome by a pan-phlebo RT-PCR assay. Aedes mosquito pools (n = 85) were further screened by nested RT-PCR assay. Sera from sheep (n = 13), goats (n = 259) and wild ungulates (n = 285) were screened for RVFV antibodies by ELISA while genome detection in pooled sera (n = 276) from domestic (n = 248) and wild ungulates (n = 37) was performed by real-time RT-PCR assay. To examine the association between the long inter-epizootic period and climatic variables, we examined El Niño-Southern Oscillation indices, precipitation anomalies, and normalized difference vegetation index. We then derived RVF risk maps by exploring climatic variables that would favor emergence of primary RVFV vectors. While no RVFV genome could be detected in pooled mosquito and serum samples, seroprevalence was significantly high (OR = 8.13, 95% CI [4.63-14.25]) in wild ungulates (33.7%; 96/285) compared to domestic ruminants (5.6%; 16/272). Retrospective analysis of RVF epizootics in Zambia showed a positive correlation between anomalous precipitation (La Niña) and disease emergence. On risk mapping, whilst northern and eastern parts of the country were at high risk, domestic ruminant population density was low (< 21 animals/km2) in these areas compared to low risk areas (>21 animals/km2). Besides evidence of silent circulation of RVFV and the risk of disease emergence in some areas, wildlife may play a role in the maintenance of RVFV in Zambia.

Autochthonous Leishmania infantum in Dogs, Zambia, 2021.

Leishmaniases are neglected tropical diseases of humans and animals. We detected Leishmania infantum in 3 mixed-breed dogs in Zambia that had no travel history outside the country. Our findings suggest presence of and probable emergence of leishmaniasis in Zambia, indicating the need for physicians and veterinarians to consider the disease during diagnosis.

Echinococcus ortleppi and Echinococcus canadensis G6/7 affect domestic animals in western Zambia.

Cystic echinococcosis (CE) is endemic in many parts of sub-Saharan Africa. In contrast to the eastern part of the continent, very little data exists on the current disease situation in southern Africa including Zambia. This study determined frequency and species identity of Echinococcus spp. circulating in livestock and dogs in the Western Province of Zambia. Cysts were collected in slaughterhouses at meat inspection (cattle) and during examination of home slaughtered pigs, while dog faecal samples were collected per-rectum and examined microscopically for the presence of taeniid eggs. Individual taeniid eggs from faecal samples and individual protoscoleces from cysts were genotyped by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) and/or sequencing of the NADH-dehydrogenase subunit 1 (nad1) and cytochrome C oxidase 1 (cox1) gene. Fifty-four of 2000 cattle (2.7%) were found infected with a total of 65 cysts, predominantly fertile lungs cysts; all cysts were identified as Echinococcus ortleppi. Two out of 52 home-slaughtered pigs (3.8%) were infected with a fertile lung cyst each; both cysts were also identified as E. ortleppi. Microscopic examination revealed 10/289 dog faecal samples to contain taeniid eggs, of which four samples (two each) contained Echinococcus canadensis (G6/7) or Taenia hydatigena, respectively. This is the first insight in the Echinococcus species circulating in Zambia providing premises for further studies into transmission dynamics of CE in the southern African region.

Prevalence of bovine fascioliasis and economic impact associated with liver condemnation in abattoirs in Mongu district of Zambia.

BACKGROUND: Fascioliasis is a trematode zoonotic snail-borne disease of public health and economic importance. The disease causes liver damage and is hardly recognized by medical personnel hence, is rarely considered as the differential diagnosis. In animals, the disease leads to mortalities, growth retardation, drop in livestock production and condemnation of the infected livers during meat inspection. The cross-sectional study was conducted from 2013 to 2017 in abattoirs in Mongu district, Western province of Zambia. Each selected carcass was examined macroscopically for bovine fascioliasis by dissecting the liver and checking for adult liver flukes. Infested and condemned livers were weighed and incinerated. RESULTS: A total of 69,152 carcasses with their livers was examined at the abattoirs for adult Fasciola worms and 44,511 (64.4%) were positive. According to the intensity of pathological lesions, 55.3% constituted severely affected livers, 30.3% were moderately affected livers and 14.4% were lightly affected livers. Our observation revealed that the most prevalent liver fluke identified was Fasciola gigantica (56.1%) and it mostly affected the poor body conditioned animals (71.4%). The study also indicated that 164,600 kg liver was condemned and destroyed. This reduced the income base for small-scale livestock farmers to about ZMW 7,407,000.00, which was equivalent to 592,560 USD. CONCLUSION: In conclusion, our study suggests that the prevalence of bovine fascioliasis was high resulting in a large amount of liver being condemned and destroyed, leading to economic losses for affected livestock farmers in the area. Consequently, there is a need to take the necessary measures to control the disease and create awareness among medical personnel to consider it as a differential diagnosis in all functional liver deficiencies due to the zoonotic nature of the disease.

A Cross-Sectional Study Investigating Cystic Hydatidosis in Slaughtered Cattle of Western Province in Zambia.

A cross-sectional study was conducted from October 2007 to November 2008 to estimate the prevalence of hydatidosis in slaughtered cattle from two abattoirs in Mongu, Western Province, Zambia, using prospective and retrospective data. Out of the 4061 cattle examined during postmortem inspection, 84 (2.1%) were positive for hydatidosis. No cases were detected from Kaoma and Shangombo districts; however, prevalence ranged from 0.6% to 2.5% in districts where it was present. Sex was found to be positively associated with hydatidosis (P = 0.035) with female cattle being more likely to have hydatidosis (OR = 1.62). In the retrospective study (1994 to 2007), annual prevalence of hydatidosis ranged from 1.56% (n = 12,641) in 2006 to 4.7% (n = 2633) in 2001 with an overall prevalence of 3% (4689/158,456). This value is comparable to that observed in cattle slaughtered between October 2007 and November 2008 (2.1%). Hydatidosis was observed in the lungs (51.2%), liver (47.6%), and kidneys (1.2%). The percentage of viable cysts was 43.7%. This study confirms the presence of hydatidosis in cattle in Western Province of Zambia and estimates economic losses due to organ condemnations. Data presented herein provides a useful baseline for developing policy and intervention measures.

The effect of seasonal variation on anthrax epidemiology in the upper Zambezi floodplain of western Zambia.

Anthrax has become endemic throughout the upper Zambezi floodplain located in the Western Province of Zambia over the recent years. To date, no comprehensive study has been carried out to determine whether recurrence of anthrax outbreaks may be linked to differences in precipitation and human activities. Retrospective data for the period 1999 to 2007 showed that a total of 1,216 bovine cases of anthrax were reported. During the same period, 1,790 human anthrax cases and a corresponding case fatality rate of 4.63% (83/1,790) was documented in the upper Zambezi floodplain. Occurrence of human cases was highly correlated with cattle outbreaks (r = 0.94, p < 0.001). Differences in precipitation were significantly associated with the occurrence of anthrax outbreaks (χ(2) = 4.75, p < 0.03), indicating that the likelihood of outbreaks occurring was higher during the dry months when human occupancy of the floodplain was greater compared to the flooding months when people and livestock moved out of this region. Human dependency on the floodplain was shown to significantly influence the epidemiology of anthrax in the upper Zambezi floodplain of western Zambia. Methods for mitigating anthrax outbreaks by disrupting the cycle of transmission are herein highlighted.

Risk analysis of an anthrax outbreak in cattle and humans of Sesheke district of Western Zambia.

An anthrax outbreak occurred in November 2010 in five villages of Sesheke district in Western Zambia. Control measures and data collection was carried out immediately the outbreak was reported. The prevalence of the disease in cattle was estimated at 7.4% (45/609) while the average herd size of infected cattle in affected villages was estimated at 121.8 (95% CI 48.8-194.8). Individual mortality per herd varied between 1.70% (3/179) and 20.25% (6/79). The relative risk of infection of cattle in the five affected villages varied between 0.18 (95% CI 0.4-5.7) and 3.7 (95% CI 1.99-6.68). In humans, the disease only affected three people and was characterized by cutaneous carbuncles. The ratio of infected persons per number of infected carcasses varied between 1:37 and 1:49 in affected villages while the overall ratio of people at risk to the number of carcasses was 42:1 indicating that despite availability of a large number of carcasses, human contact with infected carcasses was low. The findings of this study underline the importance of timely disease control measures in reducing the risk of human infections to anthrax in the face of an outbreak.